Inkjet printhead with integrated circuit mounted on polymer sealing film

ABSTRACT

A printhead for an inkjet printer, the printhead comprising: a printhead integrated circuit formed on a wafer substrate using lithographically masked etching and deposition techniques; an integrated circuit support structure for mounting in the printer adjacent a media feed path; and, a polymer sealing film between the integrated circuit support structure and the printhead integrated circuit for fixing the printhead integrated circuit to the integrated circuit support structure.

The present application is a Continuation-In-Part application of U.S.Ser. No. 10/760,254 filed on Jan. 21, 2004. In the interests of brevity,the disclosure of the parent application is incorporated in its entiretyinto the present specification by cross reference.

FIELD OF THE INVENTION

The present invention relates to printers and in particular inkjetprinters. Specific aspects of the invention relate to cartridges forprinters, printhead design and maintenance, as well as other facets ofprinter operation.

CO-PENDING APPLICATIONS

The following applications have been filed by the Applicantsimultaneously with the present application: RRB001US RRB002US RRB003USRRB004US RRB005US RRB006US RRB007US RRB008US RRB009US RRB010US RRB011USRRB012US RRB013US RRB014US RRB015US RRB016US RRB017US RRB018US RRB019USRRB020US RRB021US RRB022US RRB023US RRB024US RRB025US RRB026US RRB027USRRB030US RRB031US RRB032US RRB033US RRC001US RRC002US RRC003US RRC004USRRC005US RRC006US RRC007US RRC008US RRC009US RRC010US RRC011US RRC012USRRC013US RRC014US RRC015US RRC016US RRC017US RRC018US RRC019US RRC021USMFA001US VPA001US VPA002US PNA001US WPA001US SHA001US

The disclosures of these co-pending applications are incorporated hereinby reference. The above applications have been identified by theirfiling docket number, which will be substituted with the correspondingapplication number, once assigned.

CROSS REFERENCES TO RELATED APPLICATIONS

The following patents or patent applications filed by the applicant orassignee of the present invention are hereby incorporated bycross-reference. 6,795,215 10/884,881 PEC01NP 09/575,109 10/296,53509/575,110 6,805,419 09/607,985 6,398,332 6,394,573 6,622,923 6,747,76010/189,459 PEC14US PEC15US 10/727,181 10/727,162 10/727,163 10/727,24510/727,204 10/727,233 10/727,280 10/727,157 10/727,178 10/727,21010/727,257 10/727,238 10/727,251 10/727,159 10/727,180 10/727,17910/727,192 10/727,274 10/727,164 10/727,161 10/727,198 10/727,15810/754,536 10/754,938 10/727,227 10/727,160 PEA29US 10/854,52110/854,522 10/854,488 10/854,487 10/854,503 10/854,504 10/854,50910/854,510 10/854,496 10/854,497 10/854,495 10/854,498 10/854,51110/854,512 10/854,525 10/854,526 10/854,516 10/854,508 10/854,50710/854,515 10/854,506 10/854,505 10/854,493 10/854,494 10/854,48910/854,490 10/854,492 10/854,491 10/854,528 10/854,523 10/854,52710/854,524 10/854,520 10/854,514 10/854,519 PLT036US 10/854,49910/854,501 PLT039US 10/854,502 10/854,518 10/854,517 PLT043US 10/728,80410/728,952 10/728,806 10/728,834 10/729,790 10/728,884 10/728,97010/728,784 10/728,783 10/728,925 10/728,842 10/728,803 10/728,78010/728,779 10/773,189 10/773,204 10/773,198 10/773,199 10/773,19010/773,201 10/773,191 10/773,183 10/773,195 10/773,196 10/773,18610/773,200 10/773,185 10/773,192 10/773,197 10/773,203 10/773,18710/773,202 10/773,188 10/773,194 10/773,193 10/773,184 10/760,27210/760,273 10/760,187 10/760,182 10/760,188 10/760,218 10/760,21710/760,216 10/760,233 10/760,246 10/760,212 10/760,243 10/760,20110/760,185 10/760,253 10/760,255 10/760,209 10/760,208 10/760,19410/760,238 10/760,234 10/760,235 10/760,183 10/760,189 10/760,26210/760,232 10/760,231 10/760,200 10/760,190 10/760,191 10/760,22710/760,207 10/760,181 6,746,105 6,623,101 6,406,129 6,505,916 6,457,8096,550,895 6,457,812 6,428,133 IJ52NP 10/407212 10/407207 10/68306410/683041 10/882774 10/884889 10/922890 JUM008US JUM009US JUM010US10/922884 JUM012US JUM013US JUM014US JUM015US JUM016US 10/92287110/922880 JUM019US 10/922882 JUM021US 10/922878 JUM023US 10/922876JUM025US 10/922877 10/815625 10/815624 10/815628 10/913375 10/91337310/913374 IRB004US 10/913377 10/913378 10/913380 10/913379 10/91337610/913381 IRB011US 09/575187 6727996 6591884 6439706 6760119 09/57519809/722148 09/722146 09/721861 6290349 6428155 6785016 09/60892009/721892 09/722171 09/721858 09/722142 10/171987 10/202021 10/29172410/291512 10/291554 10/659027 10/659026 10/831242 10/884885 10/88488310/901154 NPP049US NPP051US NPP052US NPP053US NPP054US NPP057US NPP058USNPP062US 10/659027 09/693301 09/575197 09/575195 09/575159 09/57513209/575123 09/575148 09/575130 09/575165 6813039 09/575118 09/57513109/575116 6816274 09/575139 09/575186 6681045 6728000 09/57514509/575192 09/575181 09/575193 09/575183 6789194 09/575150 67891916549935 09/575174 09/575163 6737591 09/575154 09/575129 09/57512409/575188 09/575189 09/575170 09/575171 09/575161 6644642 65026146622999 6669385 CAA001US CAA002US CAA003US CAA004US CAA005US CAA006USCAA007US CAA008US CAA009US CAA010US CAA011US CAA012US CAA013US CAA014USCAA015US CAA016US CAA017US CAB001US CAC001US CAD001US CAE001US CAF001USCAF002US CAF003US CAF004US

Some applications have been listed by docket numbers. These will bereplaced when application numbers are known.

BACKGROUND OF THE INVENTION

Traditionally, most commercially available inkjet printers have a printengine which forms part of the overall structure and design of theprinter. In this regard, the body of the printer unit is typicallyconstructed to accommodate the printhead and associated media deliverymechanisms, and these features are integral with the printer unit.

This is especially the case with inkjet printers that employ a printheadthat traverses back and forth across the media as the media isprogressed through the printer unit in small iterations. In such casesthe reciprocating printhead is typically mounted to the body of theprinter unit such that it can traverse the width of the printer unitbetween a media input roller and a media output roller, with the mediainput and output rollers forming part of the structure of the printerunit. With such a printer unit it may be possible to remove theprinthead for replacement, however the other parts of the print engine,such as the media transport rollers, control circuitry and maintenancestations, are typically fixed within the printer unit and replacement ofthese parts is not possible without replacement of the entire printerunit.

As well as being rather fixed in their design construction, printerunits employing reciprocating type printheads are considerably slow,particularly when performing print jobs of full colour and/or photoquality. This is due to the fact that the printhead must continuallytraverse the stationary media to deposit the ink on the surface of themedia and it may take a number of swathes of the printhead to depositone line of the image.

Recently, it has been possible to provide a printhead that extends theentire width of the print media so that the printhead can remainstationary as the media is transported past the printhead. Such systemsgreatly increase the speed at which printing can occur as the printheadno longer needs to perform a number of swathes to deposit a line of animage, but rather the printhead can deposit the ink on the media as itmoves past at high speeds. Such printheads have made it possible toperform full colour 1600 dpi printing at speeds in the vicinity of 60pages per minute, speeds previously unattainable with conventionalinkjet printers.

Such a pagewidth printhead typically requires high precision and highspeed paper movement, and as such, the entire print engine (printhead,paper handling mechanisms and control circuitry etc) must be configuredaccordingly to ensure high quality output.

Accordingly, there is a need to provide a print engine having apagewidth printhead that can be readily employed within a standard bodyof a printer unit and is constructed in a manner that ensures that allthe necessary parts of the print engine are configured in a manner thatenables consistent, high speed printing.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the present invention provides a printheadcomprising:

-   -   a printhead integrated circuit formed on a wafer substrate using        lithographically masked etching and deposition techniques;    -   an integrated circuit support structure for mounting in the        printer adjacent a media feed path; and,    -   a polymer sealing film between the integrated circuit support        structure and the printhead integrated circuit for fixing the        printhead integrated circuit to the integrated circuit support        structure.

To feed ink to the individual nozzles on the printhead integratedcircuit (IC), it is often convenient to etch channels in the reverseside of the silicon wafer substrate. These channels need to be sealedand a polymer sealing film can provide an adequate seal as well as ameans to secure the IC to a support structure. However, if the surfaceof the support structure is uneven, the seal provided by the polymerfilm can be compromised. The surface that the IC is secured to, istypically uneven because of more ink feed channels that deliver ink tothe channels in the IC. As the film seals across the open channels inthe support, it can also bulge or sag into them. The section of filmthat sags into a support structure channel runs across several of theetched channels in the printhead IC. The sagging may cause a gap betweenthe walls separating each of the etched channels. Obviously, thisbreaches the seal and allows ink to leak out of the printhead IC and orbetween etched channels. To guard against this, the polymer sealing filmshould be thick enough to account for any sagging into the supportstructure channels while maintaining the seal over the etched channelsin the IC.

The minimum thickness of the polymer sealing film will depend on anumber of factors to be discussed in detail with reference to thepreferred embodiments. However, the Applicant's analysis and testing hasshown that a polymer sealing film thickness of 25 microns is adequatefor the printhead IC's formed using lithographically masked etching anddeposition techniques. Increasing the thickness to 50, 100 or even 200microns will correspondingly increase the reliability of the sealprovided.

In some embodiments, the polymer sealing film is more than 25 micronsthick. Optionally, the polymer sealing film is more than 50 micronsthick. Optionally, the polymer sealing film is more than 100 micronsthick. Optionally, the polymer sealing film is about 200 microns thick.

In a first aspect the present invention provides a printhead for aninkjet printer, the printhead comprising:

-   -   a printhead integrated circuit formed on a wafer substrate using        lithographically masked etching and deposition techniques;    -   an integrated circuit support structure for mounting in the        printer adjacent a media feed path; and,    -   a polymer sealing film between the integrated circuit support        structure and the printhead integrated circuit for fixing the        printhead integrated circuit to the integrated circuit support        structure.

Optionally the polymer sealing film is more than 25 microns thick.

Optionally the polymer sealing film is more than 50 microns thick.

Optionally the polymer sealing film is more than 100 microns thick.

Optionally the polymer sealing film is about 200 microns thick.

In a further aspect there is provided a printhead incorporated in acartridge unit for an inkjet printer, the cartridge unit comprising:

-   -   an ink storage compartment and an ink feed system for connection        to the printhead, the printhead having an array of ink ejection        nozzles,    -   wherein the ink storage compartment has a variable storage        volume and a displaceable wall section biased to expand the        variable storage volume to generate a negative pressure therein,        such that ink does not inadvertently leak from the ink ejection        nozzles.

In a further aspect there is provided a printhead arranged to besupplied with ink by a negatively pressurized ink storage compartment,the ink storage compartment having an interface for receiving a refillunit for refilling the ink, the interface having an inlet valve biasedto its closed configuration, wherein the refill unit comprises:

-   -   a body containing a quantity of ink;    -   engagement formations for releasably engaging the interface; and    -   an inlet valve actuator for opening the inlet valve as the        refill unit engages the ink interface so that the ink in the        body is in fluid communication with the ink storage compartment.

In a further aspect there is provided a printhead incorporated in an inkcartridge having a negatively pressurized ink storage compartment thatsupplies ink to the printhead, and an interface for receiving a refillunit for refilling the ink, the interface having a normally closed inletvalve and a normally open outlet valve, both in fluid communication withthe ink storage compartment, wherein the refill unit comprises:

-   -   a body containing a quantity of ink; and    -   a docking portion having an ink outlet and valve actuator        formations, and    -   wherein during use, the docking portion releasably engages the        interface to actuate the inlet and the outlet valves so the        cartridge fills with ink from the body because of the negative        pressure in the ink storage compartment.

In a further aspect there is provided a printhead arranged to besupplied with ink by a negatively pressurized ink storage compartmentwhich is arranged to be refilled by a refill unit via a normally openoutlet valve, the refill unit comprising:

-   -   a body containing a quantity of ink;    -   engagement formations for releasably engaging the ink storage        compartment; and    -   an outlet valve actuator for closing the outlet valve as the        refill unit engages the ink storage compartment.

In a further aspect there is provided a printhead arranged to besupplied with ink by an ink storage compartment which is arranged to berefilled by a refill unit, wherein:

-   -   the printhead has an array of nozzles;    -   during use, the ink storage compartment is maintained at a        negative pressure to avoid inadvertent ink leakage from the        nozzles;    -   the refill unit comprises a body containing a quantity of ink,        an ink outlet and a repressurizing arrangement;    -   upon engagement of the refill unit with the ink storage        compartment, the repressurizing arrangement causes part of the        unit to be inwardly depressed as the ink from the body is drawn        into the ink storage compartment through the ink outlet by the        negative pressure until pressure equalization; and    -   upon subsequent disengagement of the refill unit from the ink        storage compartment, the repressurizing arrangement releases the        inwardly depressed part of the ink storage compartment to        re-establish the negative pressure.

In a further aspect there is provided a printhead incorporated in an inkcartridge for an inkjet printer, the cartridge comprising:

-   -   an ink storage compartment having opposed wall sections        connected by a flexible wall arrangement to define a variable        ink storage volume; and    -   an ink feed system for supplying for supplying ink to the        printhead which has an array of nozzles,    -   wherein one of the opposed wall sections is displaceable and        biased to expand the variable ink storage volume to create a        negative pressure in the ink storage compartment for avoiding        inadvertent ink leakage from the nozzles.

In a further aspect there is provided a printhead arranged to besupplied with ink by an ink storage compartment having an interface forreleasably engaging with a refill unit for refilling the ink, theinterface having valves for controlling ink flows into, and out of, thestorage compartment, wherein the refill unit comprises:

-   -   a body containing a quantity of ink;    -   an ink outlet; and    -   valve actuators for actuating the valves when the refill unit        engages the interface, such that the valve actuators actuate the        valve in a predetermined sequence.

In a further aspect there is provided a printhead incorporated in an inkcartridge that forms part of an inkjet printer, the printer havingcontrol circuitry and an interface for releasably engaging a refill unitfor refilling the ink cartridge, wherein the refill unit comprises:

-   -   a body containing a quantity of ink;    -   an ink outlet; and    -   a memory circuit for storing information relating to at least        one characteristic of the ink, and    -   wherein, during use, the memory circuit allows to the control        circuit to interrogate it to verify that the ink in the refill        unit is suitable for the printer.

In a further aspect there is provided a printhead, further comprising:

-   -   a nozzle plate with an array of nozzles formed therein; and    -   a printhead maintenance assembly comprising a capper to cover        the array of nozzles when the printhead is not in use and a        cleaner for engaging the nozzle plate and wiping across the        nozzles,    -   wherein the cleaner is positioned between opposing sides of the        capper.

In a further aspect there is provided a printhead, further comprising anarray of nozzles, the printhead being incorporated in an inkjet printercomprising:

-   -   a maintenance assembly for moving between a capped position        where the assembly covers the array of nozzles, and an uncapped        position spaced from the array of nozzles; and    -   a motorized drive for moving the maintenance assembly between        the capped position and the uncapped position.

In a further aspect there is provided a printhead incorporated in an inkcartridge in an inkjet printer, the ink cartridge having an interfacefor engaging an ink refill unit for replenishing the cartridge, whereinthe ink refill unit comprises:

-   -   an ink storage compartment;    -   a docking portion for engaging the interface of the cartridge,        the docking portion having a base plate with an ink outlet for        connection to an inlet port on the interface; and    -   engagement formations for releasably engaging the interface, the        engagement formations being formed on the transverse centre line        of the base plate, the centre of the ink outlet being spaced        from the transverse centre line.

In a further aspect there is provided a printhead incorporated in an inkcartridge in an inkjet printer, the ink cartridge having an interfacefor engaging an ink refill for replenishing the cartridge, an inkstorage compartment partially defined by a tubular flexible wall, and aconstriction mechanism for constricting the flexible tubular wall by apredetermined amount, wherein the ink refill unit comprises:

-   -   a body containing a quantity of ink; and    -   a docking portion for engaging the interface of the cartridge,        the docking portion having an ink outlet for connection to an        inlet port on the interface, and a plurality of constriction        actuators for actuating the constriction mechanism as the ink        refill unit engages the interface and releases the constriction        mechanism as the ink refill unit disengages the interface.

In a further aspect there is provided a printhead incorporated in an inkcartridge in an inkjet printer, the ink cartridge having an interfacefor engaging an ink refill unit for replenishing the cartridge, whereinthe ink refill unit comprises:

-   -   a body containing a quantity of ink;    -   an ink outlet for engaging a complementary ink inlet in the        interface; and    -   a spigot extending from the body for insertion in an aperture in        the interface, the lateral cross section of the spigot being        keyed to the shape defined by the aperture to ensure the ink        refill is correctly matched to the cartridge.

In a further aspect there is provided a printhead incorporated in an inkcartridge in an inkjet printer, the ink cartridge being arranged to bereplenished by an ink refill unit, the ink refill unit comprising:

-   -   a body containing ink;    -   an ink outlet for engaging a complementary ink inlet in the        cartridge; and    -   a visual indicator to provide a visual indication when a        predetermined quantity ink has flowed from the refill unit into        the cartridge.

In a further aspect there is provided a printhead incorporated in aninkjet printer comprising:

-   -   an outer casing with a hingedly mounted panel for access its        interior; and    -   a cradle housed within the outer casing for supporting an ink        cartridge, the cradle having a hingedly mounted lid that opens        to allow the ink cartridge to be inserted and removed,    -   wherein the hinge axis of the lid and the hinge axis of the        panel are parallel, and    -   the lid and the panel both open in the same direction.

In a further aspect there is provided a printhead arranged as areplaceable pagewidth printhead of an inkjet printer and to have anarray of nozzles and printhead contacts for transmitting power and printdata to the nozzles, wherein the printer comprises:

-   -   corresponding contacts for supplying the power and print data to        the printhead contacts; and    -   a selective biasing mechanism, such that the printhead contacts        and the corresponding contacts are biased into engagement during        printing and released from biased engagement when installing or        removing the printhead.

In a further aspect there is provided a printhead arranged as areplaceable pagewidth printhead of an inkjet printer and to have anarray of nozzles and printhead contacts for transmitting power and printdata to the nozzles, wherein the printer comprises:

-   -   corresponding contacts for supplying the power and print data to        the printhead contacts; and    -   a cover member for movement between open and closed positions,        and    -   wherein in the open positions, the printhead can be installed or        removed, and the cover member is in the closed positions during        printing, such that the printhead contacts and the corresponding        contacts are moved into engagement when the cover member is        moved to the closed positions, and the printhead contacts and        the corresponding contacts disengage when the cover member is        moved to the open positions.

In a further aspect there is provided a printhead incorporated in acartridge for an inkjet printer, the cartridge comprising:

-   -   at least one ink storage compartment;    -   an ink feed system for supplying ink from the or each ink        compartment to the printhead; and    -   a maintenance station for engaging the printhead to perform one        or more maintenance functions.

In a further aspect there is provided a printhead incorporated in acradle for holding an ink cartridge within an inkjet printer, thecartridge having a plurality of ink storage compartments, the cradlecomprising a plurality of interfaces respectively corresponding to theink storage compartments,

-   -   wherein each of the interfaces is configured to receive an ink        refill unit for replenishing the corresponding ink storage        compartment.

In a further aspect there is provided a printhead for an inkjet printer,wherein the printhead integrated circuit has an array of ink ejectionnozzles formed on a substrate, the printhead further comprising:

-   -   a plurality of ink feed conduits for establishing fluid        communication with at least one ink storage compartment; and    -   a polymer sealing film between the ink feed conduits and the        printhead integrated circuits, the polymer film having an array        of apertures such that the ejection nozzles are in fluid        communication with the ink feed conduits, polymer sealing film        being more than 25 microns thick.

In another aspect the present invention provides a cartridge unit for aninkjet printer, the cartridge unit comprising:

-   -   an ink storage compartment and an ink feed system for connection        to a printhead assembly with an array of ink ejection nozzles;        wherein,    -   the ink storage compartment has a variable storage volume and a        displaceable wall section biased to expand the variable storage        volume to generate a negative pressure therein; such that,    -   ink does not inadvertently leak from the ink ejection nozzles.

In another aspect the present invention provides a refill unit forrefilling a negatively pressurized ink storage compartment that suppliesink to a printhead assembly, the ink storage compartment having aninterface for receiving the refill unit, the interface having an inletvalve biased to its closed configuration, the refill unit comprising:

-   -   a body containing a quantity of ink;    -   engagement formations for releasably engaging the interface; and    -   an inlet valve actuator for opening the inlet valve as the        refill unit engages the ink interface so that the ink in the        body is in fluid communication with the ink storage compartment.

In another aspect the present invention provides an ink refill unit foran ink cartridge, the ink cartridge having a negatively pressurized inkstorage compartment that supplies ink to a printhead assembly, and aninterface for receiving the refill unit, the interface having a normallyclosed inlet valve and a normally open outlet valve, both in fluidcommunication with the ink storage compartment, the refill unitcomprising:

-   -   a body containing a quantity of ink;    -   a docking portion having an ink outlet and valve actuator        formations; wherein during use,    -   the docking portion releasably engages the interface to actuate        the inlet and the outlet valves so the cartridge fills with ink        from the body because of the negative pressure in the ink        storage compartment.

In another aspect the present invention provides a refill unit forrefilling a negatively pressurized ink storage compartment that suppliesink to a printhead assembly via a normally open outlet valve, the refillunit comprising:

-   -   a body containing a quantity of ink;    -   engagement formations for releasably engaging the ink storage        compartment; and    -   an outlet valve actuator for closing the outlet valve as the        refill unit engages the ink storage compartment.

In another aspect the present invention provides a refill unit forrefilling an ink storage compartment supplying a printhead assembly withan array of nozzles, wherein during use, the ink storage compartment ismaintained at a negative pressure to avoid inadvertent ink leakage fromthe nozzles, the refill unit comprising:

-   -   a body containing a quantity of ink;    -   an ink outlet; and    -   a repressurizing arrangement; wherein,    -   upon engagement of the refill unit with the ink storage        compartment, the repressurizing arrangement causes part of the        cartridge to be inwardly depressed as the ink from the body is        drawn into the ink storage compartment through the ink outlet by        the negative pressure until pressure equalization; and,    -   upon subsequent disengagement of the refill unit from the ink        storage compartment, the repressurizing arrangement releases the        inwardly depressed part of the ink storage compartment to        re-establish the negative pressure.

In another aspect the present invention provides an ink cartridge for aninkjet printer, the cartridge comprising:

-   -   an ink storage compartment having opposed wall sections        connected by a flexible wall arrangement to define a variable        ink storage volume; and,    -   an ink feed system for supplying for supplying ink to a        printhead with an    -   array of nozzles; wherein,        -   one of the opposed wall sections is displaceable and biased            to expand the variable ink storage volume to create a            negative pressure in the ink storage compartment for            avoiding inadvertent ink leakage from the nozzles.

In another aspect the present invention provides a refill unit forrefilling an ink storage compartment with an interface for releasablyengaging with the refill unit, the interface having valves forcontrolling ink flows into, and out of, the storage compartment, therefill unit comprising:

-   -   a body containing a quantity of ink;    -   an ink outlet; and,    -   valve actuators for actuating the valves when the refill unit        engages the interface; such that,    -   the valve actuators actuate the valve in a predetermined        sequence.

In another aspect the present invention provides a refill unit forrefilling an ink cartridge that forms part of an inkjet printer, theprinter also having a printhead, control circuitry and an interface forreleasably engaging the refill unit, the refill unit comprising:

-   -   a body containing a quantity of ink;    -   an ink outlet; and,    -   a memory circuit for storing information relating to at least        one characteristic of the ink; wherein during use,    -   the memory circuit allows to the control circuit to interrogate        it to verify that the ink in the refill unit is suitable for the        printer.

In another aspect the present invention provides a printhead maintenanceassembly for an inkjet printhead, the printhead having a nozzle platewith an array of nozzles formed therein, the printhead maintenanceassembly comprising:

-   -   a capper to cover the array of nozzles when the printhead is not        in use; and,    -   a cleaner for engaging the nozzle plate and wiping across the        nozzles; wherein,    -   the cleaner is positioned between opposing sides of the capper.

In another aspect the present invention provides an inkjet printercomprising:

-   -   a printhead with an array of nozzles;    -   a maintenance assembly for moving between a capped position        where the assembly covers the array of nozzles, and an uncapped        position spaced from the array of nozzles; and,    -   a motorized drive for moving the maintenance assembly between        the capped position and the uncapped position.

In another aspect the present invention provides an ink refill unit forreplenishing an ink cartridge in an inkjet printer, the ink cartridgehaving an interface for engaging the ink refill unit, the ink refillunit comprising:

-   -   an ink storage compartment;    -   a docking portion for engaging the interface of the cartridge,        the docking portion having a base plate with an ink outlet for        connection to an inlet port on the interface;    -   engagement formations for releasably engaging the interface, the        engagement formations being formed on the transverse centre line        of the base plate; wherein,    -   the centre of the ink outlet is spaced from the transverse        centre line.

In another aspect the present invention provides an ink refill unit forreplenishing an ink cartridge in an inkjet printer, the ink cartridgehaving an interface for engaging the ink refill, an ink storagecompartment partially defined by a tubular flexible wall, and aconstriction mechanism for constricting the flexible tubular wall by apredetermined amount, the ink refill unit comprising:

-   -   a body containing a quantity of ink;    -   a docking portion for engaging the interface of the cartridge,        the docking portion having an ink outlet for connection to an        inlet port on the interface, and a plurality of constriction        actuators for actuating the constriction mechanism as the ink        refill unit engages the interface and releases the constriction        mechanism as the ink refill unit disengages the interface.

In another aspect the present invention provides an ink refill unit forreplenishing an ink cartridge in an inkjet printer, the ink cartridgehaving an interface for engaging the ink refill unit, the ink refillunit comprising:

-   -   a body containing a quantity of ink;    -   an ink outlet for engaging a complementary ink inlet in the        interface; and,    -   a spigot extending from the body for insertion in an aperture in        the interface; wherein,    -   the lateral cross section of the spigot is keyed to the shape        defined by the aperture to ensure the ink refill is correctly        matched to the cartridge.

In another aspect the present invention provides an ink refill unit forreplenishing an ink cartridge in an inkjet printer, the ink refill unitcomprising:

-   -   a body containing ink;    -   an ink outlet for engaging a complementary ink inlet in the        cartridge; and,    -   a visual indicator to provide a visual indication when a        predetermined quantity ink has flowed from the refill unit into        the cartridge.

In another aspect the present invention provides an inkjet printercomprising:

-   -   an outer casing with a hingedly mounted panel for access its        interior;    -   a cradle housed within the outer casing for supporting an ink        cartridge, the cradle having a hingedly mounted lid that opens        to allow the ink cartridge to be inserted and removed; wherein,    -   the hinge axis of the lid and the hinge axis of the panel are        parallel; and,    -   the lid and the panel both open in the same direction.

In another aspect the present invention provides an inkjet printercomprising:

-   -   a replaceable pagewidth printhead with an array of nozzles and        printhead contacts for transmitting power and print data to the        nozzles; and,    -   corresponding contacts for supplying the power and print data to        the printhead contacts; and,    -   a selective biasing mechanism; such that,    -   the printhead contacts and the corresponding contacts are biased        into engagement during printing and released from biased        engagement when installing or removing the printhead.

In another aspect the present invention provides an inkjet printercomprising:

-   -   a replaceable pagewidth printhead with an array of nozzles and        printhead contacts for transmitting power and print data to the        nozzles; and,    -   corresponding contacts for supplying the power and print data to        the printhead contacts; and,    -   a cover member for movement between open and closed positons;        wherein,    -   in the open positons, the printhead can be installed or removed,        and the cover member is in the closed positons during printing;        such that,    -   the printhead contacts and the corresponding contacts are moved        into engagement when the cover member is moved to the closed        positons, and the printhead contacts and the corresponding        contacts disengage when the cover member is moved to the open        positons.

In another aspect the present invention provides a cartridge for aninkjet printer, the cartridge comprising:

-   -   at least one ink storage compartment;    -   an ink feed system for supplying ink from the or each ink        compartment to a printhead; and,    -   a maintenance station for engaging the printhead to perform one        or more maintenance functions.

In another aspect the present invention provides a cradle for holding anink cartridge within an inkjet printer, the cartridge having a pluralityof ink storage compartments, the cradle comprising:

-   -   a plurality of interfaces respectively corresponding to the ink        storage compartments; wherein,    -   each of the interfaces is configured to receive an ink refill        unit for replenishing the corresponding ink storage compartment.

In another aspect the present invention provides a printhead comprising:

-   -   A printhead integrated circuit formed on a wafer substrate using        lithographically masked etching and deposition techniques;    -   An integrated circuit support structure for mounting in the        printer adjacent a media feed path; and,    -   A polymer sealing film between the integrated circuit support        structure and the printhead integrated circuit for fixing the        printhead integrated circuit to the integrated circuit support        structure.

In another aspect the present invention provides a printhead for aninkjet printer, the printhead comprising:

-   -   a printhead integrated circuit having an array of ink ejection        nozzles formed on a substrate;    -   a plurality of ink feed conduits for establishing fluid        communication with at least one ink storage compartment; and,    -   a polymer sealing film between the ink feed conduits and the        printhead integrated circuits, the polymer film having an array        of apertures such that the ejection nozzles are in fluid        communication with the ink feed conduits; wherein,    -   the polymer sealing film is more than 25 microns thick.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only, withreference to the preferred embodiments shown in the accompanyingfigures, in which:

FIG. 1 shows a front perspective view of a printer with paper in theinput tray and the collection tray extended;

FIG. 2 shows the printer unit of FIG. 1 (without paper in the input trayand with the collection tray retracted) with the casing open to exposethe interior;

FIG. 3 shows a schematic of document data flow in a printing systemaccording to one embodiment of the present invention;

FIG. 4 shows a more detailed schematic showing an architecture used inthe printing system of FIG. 3;

FIG. 5 shows a block diagram of an embodiment of the control electronicsas used in the printing system of FIG. 3;

FIG. 6 shows a perspective view of a cradle unit with open coverassembly and cartridge unit removed therefrom;

FIG. 7 shows the cradle unit of FIG. 6 with the cover assembly in itsclosed position;

FIG. 8 shows a front perspective view of the cartridge unit of FIG. 6;

FIG. 9 shows an exploded perspective view of the cartridge unit of FIG.8;

FIG. 10 shows an exploded front perspective view of the main body of thecartridge unit shown in FIG. 9;

FIG. 11 shows a bottom perspective view of the ink storage moduleassembly that locates in the main body shown in FIG. 9;

FIG. 12 shows an exploded perspective view of one of the ink storagemodules shown in FIG. 11;

FIG. 13 shows a bottom perspective view of an ink storage module shownin FIG. 12;

FIG. 14 shows a top perspective view of an ink storage module shown inFIG. 12;

FIG. 15 shows a top perspective view of the printhead assembly shown inFIG. 9;

FIG. 16 shows an exploded view of the printhead assembly shown in FIG.15;

FIG. 17 shows an inverted exploded view of the printhead assembly shownin FIG. 15;

FIG. 18 shows a cross-sectional end view of the printhead assembly ofFIG. 15;

FIG. 19 shows a magnified partial perspective view of the drop triangleend of a printhead integrated circuit module as shown in FIGS. 16 to 18;

FIG. 20 shows a magnified perspective view of the join between twoprinthead integrated circuit modules shown in FIGS. 16 to 19;

FIG. 21 shows an underside view of the printhead integrated circuitshown in FIG. 19;

FIG. 22A shows a transparent top view of a printhead assembly of FIG. 15showing in particular, the ink conduits for supplying ink to theprinthead integrated circuits;

FIG. 22B is a partial enlargement of FIG. 22A;

FIG. 23 shows a vertical sectional view of a single nozzle for ejectingink, for use with the invention, in a quiescent state;

FIG. 24 shows a vertical sectional view of the nozzle of FIG. 23 duringan initial actuation phase;

FIG. 25 shows a vertical sectional view of the nozzle of FIG. 24 laterin the actuation phase;

FIG. 26 shows a perspective partial vertical sectional view of thenozzle of FIG. 23, at the actuation state shown in FIG. 25;

FIG. 27 shows a perspective vertical section of the nozzle of FIG. 23,with ink omitted;

FIG. 28 shows a vertical sectional view of the of the nozzle of FIG. 27;

FIG. 29 shows a perspective partial vertical sectional view of thenozzle of FIG. 23, at the actuation state shown in FIG. 24;

FIG. 30 shows a plan view of the nozzle of FIG. 23;

FIG. 31 shows a plan view of the nozzle of FIG. 23 with the lever armand movable nozzle removed for clarity;

FIG. 32 shows a perspective vertical sectional view of a part of aprinthead chip incorporating a plurality of the nozzle arrangements ofthe type shown in FIG. 23;

FIG. 33 shows a schematic cross-sectional view through an ink chamber ofa single nozzle for injecting ink of a bubble forming heater elementactuator type.

FIGS. 34A to 34C show the basic operational principles of a thermal bendactuator;

FIG. 35 shows a three dimensional view of a single ink jet nozzlearrangement constructed in accordance with FIG. 34;

FIG. 36 shows an array of the nozzle arrangements shown in FIG. 35;

FIG. 37 shows a schematic showing CMOS drive and control blocks for usewith the printer of the present invention;

FIG. 38 shows a schematic showing the relationship between nozzlecolumns and dot shift registers in the CMOS blocks of FIG. 37;

FIG. 39 shows a more detailed schematic showing a unit cell and itsrelationship to the nozzle columns and dot shift registers of FIG. 38;

FIG. 40 shows a circuit diagram showing logic for a single printernozzle in the printer of the present invention;

FIG. 41 shows a front perspective view of the maintenance assembly ofthe cartridge unit shown in FIG. 9;

FIG. 42 shows an exploded front perspective view of the maintenanceassembly of FIG. 41;

FIG. 43 shows an exploded front perspective view of the underside of themaintenance assembly of FIG. 41;

FIG. 44 shows a sectional view of the maintenance assembly operationallymounted to the cartridge unit of the present invention in a cappedstate;

FIGS. 45A and 45B show front and rear perspective views of the framestructure of the cradle unit according to one embodiment of the presentinvention;

FIGS. 46A-46B show left and right perspective views of the maintenancedrive assembly of the present invention remote from the frame structureof FIGS. 45A and 45B;

FIG. 47 shows a perspective view of the support bar assembly of FIGS.45A and 45B assembled to the PCB assembly;

FIG. 48 shows a perspective side view of the arms of the support barassembly of FIG. 47 connected to a spring element associated with thecover assembly;

FIGS. 49A-49C show various views of the cradle unit according to oneembodiment of the present invention;

FIGS. 50A and 50B show sectional side views of the cradle unit with thecover assembly in a closed and open position respectively;

FIGS. 51A and 51B show top and bottom perspective views of the inkrefill unit according to one embodiment of the present invention;

FIG. 51C shows an exploded view of the ink refill unit of FIGS. 51A and51B;

FIG. 52 shows a perspective view of the ink refill unit of FIGS. 51A and51B docked with the docking ports of the cover assembly;

FIG. 53 shows a plan view of the cradle with the cartridge inside andthe cover closed;

FIG. 54A shows a cross-sectional view of the ink refill unit and theprint engine along line A-A of FIG. 53;

FIG. 54B shows a cross-sectional view of the ink refill unit and theprint engine along line B-B of FIG. 53;

FIG. 54C shows a cross-sectional view of the ink refill unit in dockingposition with the print engine along line C-C of FIG. 53; and

FIG. 54D a cross-sectional view of the ink refill unit in dockingposition with the print engine along line D-D of FIG. 53.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a printer unit 2 embodying the present invention. Mediasupply tray 3 supports and supplies media 8 to be printed by the printengine (concealed within the printer casing). Printed sheets of media 8are fed from the print engine to a media output tray 4 for collection.User interface 5 is an LCD touch screen and enables a user to controlthe operation of the printer unit 2.

FIG. 2 shows the lid 7 of the printer unit 2 open to expose the printengine 1 positioned in the internal cavity 6. Picker mechanism 9 engagesthe media in the input tray 3 (not shown for clarity) and feedsindividual streets to the print engine 1. The print engine 1 includesmedia transport means that takes the individual sheets and feeds thempast a printhead assembly (described below) for printing and subsequentdelivery to the media output tray 4 (shown retracted).

FIG. 3 schematically shows how the printer unit 2 is arranged to printdocuments received from an external source, such as a computer system702, onto a print media, such as a sheet of paper. In this regard, theprinter unit 2 includes an electrical connection with the computersystem 702 to receive pre-processed data. In the particular situationshown, the external computer system 702 is programmed to perform varioussteps involved in printing a document, including receiving the document(step 703), buffering it (step 704) and rasterizing it (step 706), andthen compressing it (step 708) for transmission to the printer unit 2.

The printer unit 2 according to one embodiment of the present invention,receives the document from the external computer system 702 in the formof a compressed, multi-layer page image, wherein control electronics 766buffers the image (step 710), and then expands the image (step 712) forfurther processing. The expanded contone layer is dithered (step 714)and then the black layer from the expansion step is composited over thedithered contone layer (step 716). Coded data may also be rendered (step718) to form an additional layer, to be printed (if desired) using aninfrared ink that is substantially invisible to the human eye. Theblack, dithered contone and infrared layers are combined (step 720) toform a page that is supplied to a printhead for printing (step 722).

In this particular arrangement, the data associated with the document tobe printed is divided into a high-resolution bi-level mask layer fortext and line art and a medium-resolution contone color image layer forimages or background colors. Optionally, colored text can be supportedby the addition of a medium-to-high-resolution contone texture layer fortexturing text and line art with color data taken from an image or fromflat colors. The printing architecture generalises these contone layersby representing them in abstract “image” and “texture” layers which canrefer to either image data or flat color data. This division of datainto layers based on content follows the base mode Mixed Raster Content(MRC) mode as would be understood by a person skilled in the art. Likethe MRC base mode, the printing architecture makes compromises in somecases when data to be printed overlap. In particular, in one form alloverlaps are reduced to a 3-layer representation in a process (collisionresolution) embodying the compromises explicitly.

FIG. 4 sets out the print data processing by the print engine controller766. As mentioned previously, data is delivered to the printer unit 2 inthe form of a compressed, multi-layer page image with the pre-processingof the image performed by a mainly software-based computer system 702.In turn, the print engine controller 766 processes this data using amainly hardware-based system.

Upon receiving the data, a distributor 730 converts the data from aproprietary representation into a hardware-specific representation andensures that the data is sent to the correct hardware device whilstobserving any constraints or requirements on data transmission to thesedevices. The distributor 730 distributes the converted data to anappropriate one of a plurality of pipelines 732. The pipelines areidentical to each other, and in essence provide decompression, scalingand dot compositing functions to generate a set of printable dotoutputs.

Each pipeline 732 includes a buffer 734 for receiving the data. Acontone decompressor 736 decompresses the color contone planes, and amask decompressor decompresses the monotone (text) layer. Contone andmask scalers 740 and 742 scale the decompressed contone and mask planesrespectively, to take into account the size of the medium onto which thepage is to be printed.

The scaled contone planes are then dithered by ditherer 744. In oneform, a stochastic dispersed-dot dither is used. Unlike a clustered-dot(or amplitude-modulated) dither, a dispersed-dot (orfrequency-modulated) dither reproduces high spatial frequencies (i.e.image detail) almost to the limits of the dot resolution, whilesimultaneously reproducing lower spatial frequencies to their full colordepth, when spatially integrated by the eye. A stochastic dither matrixis carefully designed to be relatively free of objectionablelow-frequency patterns when tiled across the image. As such, its sizetypically exceeds the minimum size required to support a particularnumber of intensity levels (e.g. 16×16×8 bits for 257 intensity levels).

The dithered planes are then composited in a dot compositor 746 on adot-by-dot basis to provide dot data suitable for printing. This data isforwarded to data distribution and drive electronics 748, which in turndistributes the data to the correct nozzle actuators 750, which in turncause ink to be ejected from the correct nozzles 752 at the correct timein a manner which will be described in more detail later in thedescription.

As will be appreciated, the components employed within the print enginecontroller 766 to process the image for printing depend greatly upon themanner in which data is presented. In this regard it may be possible forthe print engine controller 766 to employ additional software and/orhardware components to perform more processing within the printer unit 2thus reducing the reliance upon the computer system 702. Alternatively,the print engine controller 766 may employ fewer software and/orhardware components to perform less processing thus relying upon thecomputer system 702 to process the image to a higher degree beforetransmitting the data to the printer unit 2.

FIG. 5 provides a block representation of the components necessary toperform the above mentioned tasks. In this arrangement, the hardwarepipelines 732 are embodied in a Small Office Home Office Printer EngineChip (SoPEC) 766. As shown, a SoPEC device consists of 3 distinctsubsystems: a Central Processing Unit (CPU) subsystem 771, a DynamicRandom Access Memory (DRAM) subsystem 772 and a Print Engine Pipeline(PEP) subsystem 773.

The CPU subsystem 771 includes a CPU 775 that controls and configuresall aspects of the other subsystems. It provides general support forinterfacing and synchronizing all elements of the print engine 1. Italso controls the low-speed communication to QA chips (described below).The CPU subsystem 771 also contains various peripherals to aid the CPU775, such as General Purpose Input Output (GPIO, which includes motorcontrol), an Interrupt Controller Unit (ICU), LSS Master and generaltimers. The Serial Communications Block (SCB) on the CPU subsystemprovides a full speed USB 1.1 interface to the host as well as an InterSoPEC Interface (ISI) to other SoPEC devices (not shown).

The DRAM subsystem 772 accepts requests from the CPU, SerialCommunications Block (SCB) and blocks within the PEP subsystem. The DRAMsubsystem 772, and in particular the DRAM Interface Unit (DIU),arbitrates the various requests and determines which request should winaccess to the DRAM. The DIU arbitrates based on configured parameters,to allow sufficient access to DRAM for all requesters. The DIU alsohides the implementation specifics of the DRAM such as page size, numberof banks and refresh rates.

The Print Engine Pipeline (PEP) subsystem 773 accepts compressed pagesfrom DRAM and renders them to bi-level dots for a given print linedestined for a printhead interface (PHI) that communicates directly withthe printhead. The first stage of the page expansion pipeline is theContone Decoder Unit (CDU), Lossless Bi-level Decoder (LBD) and, whererequired, Tag Encoder (TE). The CDU expands the JPEG-compressed contone(typically CMYK) layers, the LBD expands the compressed bi-level layer(typically K), and the TE encodes any Netpage tags for later rendering(typically in IR or K ink), in the event that the printer unit 2 hasNetpage capabilities (see the cross referenced documents for a detailedexplanation of the Netpage system). The output from the first stage is aset of buffers: the Contone FIFO unit (CFU), the Spot FIFO Unit (SFU),and the Tag FIFO Unit (TFU). The CFU and SFU buffers are implemented inDRAM.

The second stage is the Halftone Compositor Unit (HCU), which dithersthe contone layer and composites position tags and the bi-level spotlayer over the resulting bi-level dithered layer.

A number of compositing options can be implemented, depending upon theprinthead with which the SoPEC device is used. Up to 6 channels ofbi-level data are produced from this stage, although not all channelsmay be present on the printhead. For example, the printhead may be CMYonly, with K pushed into the CMY channels and IR ignored. Alternatively,any encoded tags may be printed in K if IR ink is not available (or fortesting purposes).

In the third stage, a Dead Nozzle Compensator (DNC) compensates for deadnozzles in the printhead by color redundancy and error diffusing of deadnozzle data into surrounding dots.

The resultant bi-level 5 channel dot-data (typically CMYK, Infrared) isbuffered and written to a set of line buffers stored in DRAM via aDotline Writer Unit (DWU).

Finally, the dot-data is loaded back from DRAM, and passed to theprinthead interface via a dot FIFO. The dot FIFO accepts data from aLine Loader Unit (LLU) at the system clock rate pclk), while thePrintHead Interface (PHI) removes data from the FIFO and sends it to theprinthead at a rate of ⅔ times the system clock rate.

In the preferred form, the DRAM is 2.5 Mbytes in size, of which about 2Mbytes are available for compressed page store data. A compressed pageis received in two or more bands, with a number of bands stored inmemory. As a band of the page is consumed by the PEP subsystem 773 forprinting, a new band can be downloaded. The new band may be for thecurrent page or the next page.

Using banding it is possible to begin printing a page before thecomplete compressed page is downloaded, but care must be taken to ensurethat data is always available for printing or a buffer under-run mayoccur.

The embedded USB 1.1 device accepts compressed page data and controlcommands from the host PC, and facilitates the data transfer to eitherthe DRAM (or to another SoPEC device in multi-SoPEC systems, asdescribed below).

Multiple SoPEC devices can be used in alternative embodiments, and canperform different functions depending upon the particularimplementation. For example, in some cases a SoPEC device can be usedsimply for its onboard DRAM, while another SoPEC device attends to thevarious decompression and formatting functions described above. This canreduce the chance of buffer under-run, which can happen in the eventthat the printer commences printing a page prior to all the data forthat page being received and the rest of the data is not received intime. Adding an extra SoPEC device for its memory buffering capabilitiesdoubles the amount of data that can be buffered, even if none of theother capabilities of the additional chip are utilized.

Each SoPEC system can have several quality assurance (QA) devicesdesigned to cooperate with each other to ensure the quality of theprinter mechanics, the quality of the ink supply so the printheadnozzles will not be damaged during prints, and the quality of thesoftware to ensure printheads and mechanics are not damaged.

Normally, each printing SoPEC will have an associated printer unit QA,which stores information relating to the printer unit attributes such asmaximum print speed. The cartridge unit may also contain a QA chip,which stores cartridge information such as the amount of ink remaining,and may also be configured to act as a ROM (effectively as an EEPROM)that stores printhead-specific information such as dead nozzle mappingand printhead characteristics. The refill unit may also contain a QAchip, which stores refill ink information such as the type/colour of theink and the amount of ink present for refilling. The CPU in the SoPECdevice can optionally load and run program code from a QA Chip thateffectively acts as a serial EEPROM. Finally, the CPU in the SoPECdevice runs a logical QA chip (i.e., a software QA chip).

Usually, all QA chips in the system are physically identical, with onlythe contents of flash memory differentiating one from the other.

Each SoPEC device has two LSS system buses that can communicate with QAdevices for system authentication and ink usage accounting. A largenumber of QA devices can be used per bus and their position in thesystem is unrestricted with the exception that printer QA and ink QAdevices should be on separate LSS busses.

In use, the logical QA communicates with the ink QA to determineremaining ink. The reply from the ink QA is authenticated with referenceto the printer QA. The verification from the printer QA is itselfauthenticated by the logical QA, thereby indirectly adding an additionalauthentication level to the reply from the ink QA.

Data passed between the QA chips is authenticated by way of digitalsignatures. In the preferred embodiment, HMAC-SHA1 authentication isused for data, and RSA is used for program code, although other schemescould be used instead.

As will be appreciated, the SoPEC device therefore controls the overalloperation of the print engine 1 and performs essential data processingtasks as well as synchronising and controlling the operation of theindividual components of the print engine 1 to facilitate print mediahandling, as will be discussed below.

Print Engine

The print engine 1 is shown in detail in FIGS. 6 and 7 and consists oftwo main parts: a cartridge unit 10 and a cradle unit 12.

The cartridge unit 10 is shaped and sized to be received within thecradle unit 12 and secured in position by a cover assembly 11 mounted tothe cradle unit. The cradle unit 12 is in turn configured to be fixedwithin the printer unit 2 to facilitate printing as discussed above.

FIG. 7 shows the print engine 1 in its assembled form with cartridgeunit 10 secured in the cradle unit 12 and cover assembly 11 closed. Theprint engine 1 controls various aspects associated with printing inresponse to user inputs from the user interface 5 of the printer unit 2.These aspects include transporting the media past the printhead in acontrolled manner and the controlled ejection of ink onto the surface ofthe passing media.

Cartridge Unit

The cartridge unit 10 is shown in detail in FIGS. 8 and 9. Withreference to the exploded view of FIG. 9, the cartridge unit 10generally consists of a main body 20, an ink storage module assembly 21,a printhead assembly 22 and a maintenance assembly 23.

Each of these parts are assembled together to form an integral unitwhich combines ink storage means together with the ink ejection means.Such an arrangement ensures that the ink is directly supplied to theprinthead assembly 22 for printing, as required, and should there be aneed to replace either or both of the ink storage or the printheadassembly, this can be readily done by replacing the entire cartridgeunit 10.

However, the operating life of the printhead is not limited by thesupply of ink. The top surface 42 of the cartridge unit 10 hasinterfaces 61 for docking with a refill supply of ink to replenish theink storage modules 45 when necessary. The ink refill unit and theprocess of docking with the cartridge are discussed in greater detailbelow. To further extend the life of the printhead, the cartridge unitcarries an integral printhead maintenance assembly 23 that caps, wipesand moistens the printhead. This assembly is also described in moredetail later.

Main Body

The main body 20 of the cartridge unit 10 is shown in more detail inFIG. 10 and comprises a substantially rectangular frame 25 having anopen top and an open longitudinally extending side wall. A pair of posts26 project from the underside of the frame at either end. These posts 26are provided to mount the maintenance assembly 23 to the main body 10,in a manner described below.

An ink outlet molding 27 has ink outlets (not shown) in its undersidecorresponding to each of the ink storage modules 45 to be housed in themain body 20. Each of the ink outlets has a pair of inwardly extendingsilicone rings seals. The rings seals are co-molded with the ink outletmolding 27 and seal against the ink inlets to the printhead assemblydescribed below. The ink outlet molding 27 is ultra sonically welded tothe underside of the rectangular frame 25.

Along one longitudinal wall of the frame 25 are a series of inkdownpipes 30. Each downpipe 30 has an O-ring seal 29 at its upper end toform a sealed connection with the ink outlet of respective ink storagemodules (described below). When the ink outlet molding 27 is welded tothe body 20, each ink downpipe 30 is in fluid communication withrespective ink outlets in the underside of the molding 27.

The air sleeve 31 is connected to a pressurized air source (not shown)and provides an air flow into the printhead assembly where it isdirected across the printhead nozzles to avoid paper dust clogging(discussed further below).

Ink filing ports 35 are formed in the lower parts of each ink downpipe30. These filling ports are for the initial charging of the ink storageassemblies 21 only. Any subsequent refilling of the ink storagesassemblies, uses the ink refill units described below. To assist theinitial filling process, a vacuum is applied to the air vents 41 in thetop surface 42 of the cartridge unit 10 (see FIG. 9). The air vents 41are connected to the interior of the ink bag in each ink storage module45 (described below). Ink is fed through the filling port 35 and drawnup the ink downpipe 30 into the ink storage volume. During the fillingprocess, the cartridge unit is tilted so that the air vents 41 are thehighest point in each of the respective ink bag, and filled until thevacuum draws ink through the air vent 41. This ensures that each ink bagis completely filled and purged of air. Skilled workers in this fieldwill appreciate that air bubbles entrained with the ink flow to theprinthead can harm the operation of the nozzles.

As shown in FIGS. 15 to 17, the lower member 65 is provided with aplurality of priming inlets 85 at one end thereof. Each of the priminginlets 85 communicate directly with one of the channels 67 and providean alternative, or additional means for priming the ink storage modules45 with ink prior to shipment and use.

When the ink storage modules are full, a polymer sealing ball 33 isinserted into the filling port 35 and the air vent 41.

A metal plate 34 mounts to the underside of the frame 25 and the outletmolding 30 to provide the cartridge unit 10 with structural rigidity. Itis snap locked into place by hooking the detents 38 into slots (notshown) in the back wall of the frame 25 and rotating the plate 34 untilthe line of barbed snap lock formations 32 clip into the outer line ofapertures 37.

The plate 34 has holes 39 to receive the ink outlets (not shown) thatproject from the lower surface of the outlet molding 27. The pressedmetal plate 34 also has a flange portion 40 projecting downwardly withrespect to the frame 25, which acts as a load bearing surface discussedin more detail below.

The ink storage assembly lid 21 of the cartridge unit 10 is shown indetail in FIGS. 11 to 14. The lid 21 is configured to mate with theframe 25 of the main body 20 to form an enclosed unit. As best shown inFIG. 11, the ink storage modules 45 are mounted to the underside of thelid 21 and extend into the individual cavities 36 provided by the mainbody 20 (see FIG. 10).

One of the ink storage modules 45 is shown in isolation in FIGS. 12, 13and 14. Ink bag 46 is made from a flexible, air impermeablethermoplastic film such as Mylar® which allows ink to be retainedtherein in a pressurised state. The flexible bag 46 can expand as it isfilled with ink and collapse as ink is consumed. This is discussed inmore detail later with reference to the refilling process shown in FIGS.54A to 54D.

The ink bag 46 extends between an upper plate member 47 and a lowerplate member 48. It is heat welded (or similar) to the plates 47 and 48for an air tight seal. The upper plate member 47 is arranged to receivea valve insert 49. The valve insert has an inlet valve 16 and an outletvalve 18. The valve insert 49 is positioned such that it can communicatedirectly with a port 51 formed in the top surface 42 to receive ink froman ink refill unit, as well as an outlet 52 to deliver ink to theprinthead assembly 22. As best shown in FIG. 14, the inlet valve 15receives the ink delivery needle of an ink refill unit (discussed later)through a slit positioned in the port 51 in the upper surface 42. Theinlet valve 16 is biased closed and opens when the refill unit(described below) docks with the cartridge unit 10.

Conversely, the outlet valve 18 is biased open and closes when therefill unit docks. A filter 215 covers the entrance to the outlet valvein the upper plate member 47. The filter is sized to remove solidcontaminants and air bubbles. As discussed above, compressible airbubbles can prevent a nozzle from operating.

The outlet valve connects to a conduit 52 in the underside of the lid 21which leads to the downpipe collar 216. When the ink storage assembly 21is placed into the main body 20, the collar 216 seals over the O-ringseal 29 on the end of the downpipe 30.

The upper plate 47 is fixed to the underside of the lid 21 to hold thevalve insert 49 in position. The lower plate 48 slides within the collar57 and the inside edges of the four struts 19 extending from theunderside of the lid 21. The plate 48 slides down the struts 19 as thebag 46 fills and expands. Conversely, it slides back towards the lid 21as the bag 21 empties. The length of the bag 46 limits the travel of thelower plate 48 before it reaches the retaining bar 55. A constant forcespring 54 extends between the retaining bar 55 and the recessed peg 53to bias the plate 48 towards the retaining bar 55. In turn, this biasesthe bag 46 to expand and thereby maintains the ink within the bag at anegative pressure. This avoids ink leakage from the printhead nozzles.

Bag Constrictor.

Each ink storage module 45 has a bag constrictor 43 to re-establish thenegative pressure in the ink after each refilling operation. Theconstrictor 43 has a lower collar 57 that abuts the ends of the struts19 and is held in place by the retaining bar 55. The lower plate 48slides upwardly within lower collar 57 as the ink bag 46 empties. Fourbowed panels 58 extend upwardly from the lower collar 57 to an uppercollar 59. The panels 58 bow slightly inwards. The ink refill unit(described below) has four constrictor actuators. When the refill dockswith the cartridge unit, the constrictor actuators extend through theapertures 60 in the lid 21 to push the upper collar 59 towards the lowercollar 57. This causes the panels 58 to bow further inwards to press oneach side of the bag 46.

During refilling, the negative pressure in the ink bag 46 draws ink outof the refill unit. The negative pressure is created by the constantforce spring 54 biasing the lower plate 48 to wards the retainer bar 55.When the ink bag is full, the negative pressure disappears. Withoutnegative pressure in the ink bag 46, there is a risk of ink leakage fromthe nozzles. The negative pressure is re-established in the bag 46 whenthe refill unit is removed from the cartridge. As the four constrictoractuators retract through the apertures 60 in the lid 21, the bowedpanels 58 can push the upper collar 59 back towards the upper platemember 47. The panels 58 straighten so that they are not pressing on thesides of the bag 46 as much. This allows the bag 46 to bulge slightly,and as the inlet valve 16 is closed, the slight increase in bag volumerestores the negative pressure.

Printhead Assembly

The printhead assembly 22 is shown in more detail in FIGS. 15 to 18, andis adapted to be attached to the underside of the main body 20 toreceive ink from the outlets molding 27 (see FIG. 10).

The printhead assembly 22 generally comprises an elongate upper member62 which is configured to extends beneath the main body 20, between theposts 26. A plurality of U-shaped clips 63 project from the upper member62. These pass through the recesses 37 provided in the rigid plate 34and become captured by lugs (not shown) formed in the main body 20 tosecure the printhead assembly 22.

The upper element 62 has a plurality of feed tubes 64 that are receivedwithin the outlets in the outlet molding 27 when the printhead assembly22 secures to the main body 20. The feed tubes 64 may be provided withan outer coating to guard against ink leakage.

The upper member 62 is made from a liquid crystal polymer (LCP) whichoffers a number of advantages. It can be molded so that its coefficientof thermal expansion (CTE) is similar to that of silicon. It will beappreciated that any significant difference in the CTE's of theprinthead integrated circuit 74 (discussed below) and the underlyingmoldings can cause the entire structure to bow. However, as the CTE ofLCP in the mold direction is much less than that in the non-molddirection (˜5 ppm/° C. compared to ˜20 ppm/° C.), care must be take toensure that the mold direction of the LCP moldings is unidirectionalwith the longitudinal extent of the printhead integrated circuit (IC)74. LCP also has a relatively high stiffness with a modulus that istypically 5 times that of ‘normal plastics’ such as polycarbonates,styrene, nylon, PET and polypropylene.

As best shown in FIG. 16, upper member 62 has an open channelconfiguration for receiving a lower member 65, which is bonded thereto,via an adhesive film 66. The lower member 65 is also made from an LCPand has a plurality of ink channels 67 formed along its length. Each ofthe ink channels 67 receive ink from one of the feed tubes 64, anddistribute the ink along the length of the printhead assembly 22. Thechannels are 1 mm wide and separated by 0.75 mm thick walls.

In the embodiment shown, the lower member 65 has five channels 67extending along its length. Each channel 67 receives ink from only oneof the five feed tubes 64, which in turn receives ink from one of theink storage modules 45 (see FIG. 10) to reduce the risk of mixingdifferent coloured inks. In this regard, adhesive film 66 also acts toseal the individual ink channels 67 to prevent cross channel mixing ofthe ink when the lower member 65 is assembled to the upper member 62.

In the bottom of each channel 67 are a series of equi-spaced holes 69(best seen in FIG. 17) to give five rows of holes 69 in the bottomsurface of the lower member 65. The middle row of holes 69 extends alongthe centre-line of the lower member 65, directly above the printhead IC74. As best seen in FIG. 22A, other rows of holes 69 on either side ofthe middle row need conduits 70 from each hole 69 to the centre so thatink can be fed to the printhead IC 74.

Referring to FIG. 18, the printhead IC 74 is mounted to the underside ofthe lower member 65 by a polymer sealing film 71. This film may be athermoplastic film such as a PET or Polysulphone film, or it may be inthe form of a thermoset film, such as those manufactured by ALtechnologies and Rogers Corporation. The polymer sealing film 71 is alaminate with adhesive layers on both sides of a central film, andlaminated onto the underside of the lower member 65. As shown in FIGS.17, 22A and 22B, a plurality of holes 72 are laser drilled through theadhesive film 71 to coincide with the centrally disposed ink deliverypoints (the middle row of holes 69 and the ends of the conduits 70) forfluid communication between the printhead IC 74 and the channels 67.

The thickness of the polymer sealing film 71 is critical to theeffectiveness of the ink seal it provides. As best seen in FIGS. 21 to22B, the polymer sealing film seals the etched channels 77 on thereverse side of the printhead IC 74, as well as the conduits 70 on theother side of the film. However, as the film 71 seals across the openend of the conduits 70, it can also bulge or sag into the conduit. Thesection of film that sags into a conduit 70 runs across several of theetched channels 77 in the printhead IC 74. The sagging may cause a gapbetween the walls separating each of the etched channels 77. Obviously,this breaches the seal and allows ink to leak out of the printhead IC 74and or between etched channels 77.

To guard against this, the polymer sealing film 71 should be thickenough to account for any sagging into the conduits 70 while maintainingthe seal over the etched channels 77. The minimum thickness of thepolymer sealing film 71 will depend on:

-   -   1. the width of the conduit into which it sags;    -   2. the thickness of the adhesive layers in the film's laminate        structure;    -   3. the ‘stiffness’ of the adhesive layer as the printhead IC 74        is being pushed into it; and,    -   4. the modulus of the central film material of the laminate.

A polymer sealing film 71 thickness of 25 microns is adequate for theprinthead assembly 22 shown. However, increasing the thickness to 50,100 or even 200 microns will correspondingly increase the reliability ofthe seal provided.

Ink delivery inlets 73 are formed in the ‘front’ surface of a printheadIC 74. The inlets 73 supply ink to respective nozzles 801 (describedbelow with reference to FIGS. 23 to 36) positioned on the inlets. Theink must be delivered to the IC's so as to supply ink to each and everyindividual inlet 73. Accordingly, the inlets 73 within an individualprinthead IC 74 are physically grouped to reduce ink supply complexityand wiring complexity. They are also grouped logically to minimize powerconsumption and allow a variety of printing speeds.

Each printhead IC 74 is configured to receive and print five differentcolours of ink (C, M, Y, K and IR) and contains 1280 ink inlets percolour, with these nozzles being divided into even and odd nozzles (640each). Even and odd nozzles for each colour are provided on differentrows on the printhead IC 74 and are aligned vertically to perform true1600 dpi printing, meaning that nozzles 801 are arranged in 10 rows, asclearly shown in FIG. 19. The horizontal distance between two adjacentnozzles 801 on a single row is 31.75 microns, whilst the verticaldistance between rows of nozzles is based on the firing order of thenozzles, but rows are typically separated by an exact number of dotlines, plus a fraction of a dot line corresponding to the distance thepaper will move between row firing times. Also, the spacing of even andodd rows of nozzles for a given colour must be such that they can sharean ink channel, as will be described below.

As alluded to previously, the present invention is related to page-widthprinting and as such the printhead ICs 74 are arranged to extendhorizontally across the width of the printhead assembly 22. To achievethis, individual printhead ICs 74 are linked together in abuttingarrangement across the surface of the adhesive layer 71, as shown inFIGS. 16 and 17. The printhead IC's 74 may be attached to the polymersealing film 71 by heating the IC's above the melting point of theadhesive layer and then pressing them into the sealing film 71, ormelting the adhesive layer under the IC with a laser before pressingthem into the film. Another option is to both heat the IC (not above theadhesive melting point) and the adhesive layer, before pressing it intothe film 71.

The length of an individual printhead IC 74 is around 20-22 mm. To printan A4/US letter sized page, 11-12 individual printhead ICs 74 arecontiguously linked together. The number of individual printhead ICs 74may be varied to accommodate sheets of other widths.

The printhead ICs 74 may be linked together in a variety of ways. Oneparticular manner for linking the ICs 74 is shown in FIG. 20. In thisarrangement, the ICs 74 are shaped at their ends to link together toform a horizontal line of ICs, with no vertical offset betweenneighboring ICs. A sloping join is provided between the ICs havingsubstantially a 45° angle. The joining edge is not straight and has asawtooth profile to facilitate positioning, and the ICs 74 are intendedto be spaced about 11 microns apart, measured perpendicular to thejoining edge. In this arrangement, the left most ink delivery nozzles 73on each row are dropped by 10 line pitches and arranged in a triangleconfiguration. This arrangement provides a degree of overlap of nozzlesat the join and maintains the pitch of the nozzles to ensure that thedrops of ink are delivered consistently along the printing zone. Thisarrangement also ensures that more silicon is provided at the edge ofthe IC 74 to ensure sufficient linkage. Whilst control of the operationof the nozzles is performed by the SoPEC device (discussed later in thedescription), compensation for the nozzles may be performed in theprinthead, or may also be performed by the SoPEC device, depending onthe storage requirements. In this regard it will be appreciated that thedropped triangle arrangement of nozzles disposed at one end of the IC 74provides the minimum on-printhead storage requirements. However wherestorage requirements are less critical, shapes other than a triangle canbe used, for example, the dropped rows may take the form of a trapezoid.

The upper surface of the printhead ICs have a number of bond pads 75provided along an edge thereof which provide a means for receiving dataand or power to control the operation of the nozzles 73 from the SoPECdevice. To aid in positioning the ICs 74 correctly on the surface of theadhesive layer 71 and aligning the ICs 74 such that they correctly alignwith the holes 72 formed in the adhesive layer 71, fiducials 76 are alsoprovided on the surface of the ICs 74. The fiducials 76 are in the formof markers that are readily identifiable by appropriate positioningequipment to indicate the true position of the IC 74 with respect to aneighbouring IC and the surface of the adhesive layer 71, and arestrategically positioned at the edges of the ICs 74, and along thelength of the adhesive layer 71.

In order to receive the ink from the holes 72 formed in the polymersealing film 71 and to distribute the ink to the ink inlets 73, theunderside of each printhead IC 74 is configured as shown in FIG. 21. Anumber of etched channels 77 are provided, with each channel 77 in fluidcommunication with a pair of rows of inlets 73 dedicated to deliveringone particular colour or type of ink. The channels 77 are about 80microns wide, which is equivalent to the width of the holes 72 in thepolymer sealing film 71, and extend the length of the IC 74. Thechannels 77 are divided into sections by silicon walls 78. Each sectionsis directly supplied with ink, to reduce the flow path to the inlets 73and the likelihood of ink starvation to the individual nozzles 801. Inthis regard, each section feeds approximately 128 nozzles 801 via theirrespective inlets 73.

FIG. 22B shows more clearly how the ink is fed to the etched channels 77formed in the underside of the ICs 74 for supply to the nozzles 73. Asshown, holes 72 formed through the polymer sealing film 71 are alignedwith one of the channels 77 at the point where the silicon wall 78separates the channel 77 into sections. The holes 72 are about 80microns in width which is substantially the same width of the channels77 such that one hole 72 supplies ink to two sections of the channel 77.It will be appreciated that this halves the density of holes 72 requiredin the polymer sealing film 71.

Following attachment and alignment of each of the printhead ICs 74 tothe surface of the polymer sealing film 71, a flex PCB 79 (see FIG. 18)is attached along an edge of the ICs 74 so that control signals andpower can be supplied to the bond pads 75 to control and operate thenozzles 801. As shown more clearly in FIG. 15, the flex PCB 79 extendsfrom the printhead assembly 22 and folds around the printhead assembly22.

The flex PCB 79 may also have a plurality of decoupling capacitors 81arranged along its length for controlling the power and data signalsreceived. As best shown in FIG. 16, the flex PCB 79 has a plurality ofelectrical contacts 180 formed along its length for receiving power andor data signals from the control circuitry of the cradle unit 12. Aplurality of holes 80 are also formed along the distal edge of the flexPCB 79 which provide a means for attaching the flex PCB to the flangeportion 40 of the rigid plate 34 of the main body 20. The manner inwhich the electrical contacts of the flex PCB 79 contact the power anddata contacts of the cradle unit 12 will be described later.

As shown in FIG. 18, a media shield 82 protects the printhead ICs 74from damage which may occur due to contact with the passing media. Themedia shield 82 is attached to the upper member 62 upstream of theprinthead ICs 74 via an appropriate clip-lock arrangement or via anadhesive. When attached in this manner, the printhead ICs 74 sit belowthe surface of the media shield 82, out of the path of the passingmedia.

A space 83 is provided between the media shield 82 and the upper 62 andlower 65 members which can receive pressurized air from an aircompressor or the like. As this space 83 extends along the length of theprinthead assembly 22, compressed air can be supplied to the space 56from either end of the printhead assembly 22 and be evenly distributedalong the assembly. The inner surface of the media shield 82 is providedwith a series of fins 84 which define a plurality of air outlets evenlydistributed along the length of the media shield 82 through which thecompressed air travels and is directed across the printhead ICs 74 inthe direction of the media delivery. This arrangement acts to preventdust and other particulate matter carried with the media from settlingon the surface of the printhead ICs, which could cause blockage anddamage to the nozzles.

Ink Delivery Nozzles

One example of a type of ink delivery nozzle arrangement suitable forthe present invention, comprising a nozzle and corresponding actuator,will now be described with reference to FIGS. 23 to 32. FIG. 32 shows anarray of ink delivery nozzle arrangements 801 formed on a siliconsubstrate 8015. Each of the nozzle arrangements 801 are identical,however groups of nozzle arrangements 801 are arranged to be fed withdifferent colored inks or fixative. In this regard, the nozzlearrangements are arranged in rows and are staggered with respect to eachother, allowing closer spacing of ink dots during printing than would bepossible with a single row of nozzles. Such an arrangement makes itpossible to provide a high density of nozzles, for example, more than5000 nozzles arrayed in a plurality of staggered rows each having aninterspacing of about 32 microns between the nozzles in each row andabout 80 microns between the adjacent rows. The multiple rows also allowfor redundancy (if desired), thereby allowing for a predeterminedfailure rate per nozzle.

Each nozzle arrangement 801 is the product of an integrated circuitfabrication technique. In particular, the nozzle arrangement 801 definesa micro-electromechanical system (MEMS).

For clarity and ease of description, the construction and operation of asingle nozzle arrangement 801 will be described with reference to FIGS.23 to 31.

The ink jet printhead integrated circuit 74 includes a silicon wafersubstrate 8015 having 0.35 micron 1 P4M 12 volt CMOS microprocessingelectronics is positioned thereon.

A silicon dioxide (or alternatively glass) layer 8017 is positioned onthe substrate 8015. The silicon dioxide layer 8017 defines CMOSdielectric layers. CMOS top-level metal defines a pair of alignedaluminium electrode contact layers 8030 positioned on the silicondioxide layer 8017. Both the silicon wafer substrate 8015 and thesilicon dioxide layer 8017 are etched to define an ink inlet channel8014 having a generally circular cross section (in plan). An aluminiumdiffusion barrier 8028 of CMOS metal 1, CMOS metal 2/3 and CMOS toplevel metal is positioned in the silicon dioxide layer 8017 about theink inlet channel 8014. The diffusion barrier 8028 serves to inhibit thediffusion of hydroxyl ions through CMOS oxide layers of the driveelectronics layer 8017.

A passivation layer in the form of a layer of silicon nitride 8031 ispositioned over the aluminium contact layers 8030 and the silicondioxide layer 8017. Each portion of the passivation layer 8031positioned over the contact layers 8030 has an opening 8032 definedtherein to provide access to the contacts 8030.

The nozzle arrangement 801 includes a nozzle chamber 8029 defined by anannular nozzle wall 8033, which terminates at an upper end in a nozzleroof 8034 and a radially inner nozzle rim 804 that is circular in plan.The ink inlet channel 8014 is in fluid communication with the nozzlechamber 8029. At a lower end of the nozzle wall, there is disposed amoving rim 8010, that includes a moving seal lip 8040. An encirclingwall 8038 surrounds the movable nozzle, and includes a stationary seallip 8039 that, when the nozzle is at rest as shown in FIG. 26, isadjacent the moving rim 8010. A fluidic seal 8011 is formed due to thesurface tension of ink trapped between the stationary seal lip 8039 andthe moving seal lip 8040. This prevents leakage of ink from the chamberwhilst providing a low resistance coupling between the encircling wall8038 and the nozzle wall 8033.

As best shown in FIG. 30, a plurality of radially extending recesses8035 is defined in the roof 8034 about the nozzle rim 804. The recesses8035 serve to contain radial ink flow as a result of ink escaping pastthe nozzle rim 804.

The nozzle wall 8033 forms part of a lever arrangement that is mountedto a carrier 8036 having a generally U-shaped profile with a base 8037attached to the layer 8031 of silicon nitride.

The lever arrangement also includes a lever arm 8018 that extends fromthe nozzle walls and incorporates a lateral stiffening beam 8022. Thelever arm 8018 is attached to a pair of passive beams 806, formed fromtitanium nitride (TiN) and positioned on either side of the nozzlearrangement, as best shown in FIGS. 26 and 31. The other ends of thepassive beams 806 are attached to the carrier 8036.

The lever arm 8018 is also attached to an actuator beam 807, which isformed from TiN. It will be noted that this attachment to the actuatorbeam is made at a point a small but critical distance higher than theattachments to the passive beam 806.

As best shown in FIGS. 23 and 29, the actuator beam 807 is substantiallyU-shaped in plan, defining a current path between the electrode 809 andan opposite electrode 8041. Each of the electrodes 809 and 8041 areelectrically connected to respective points in the contact layer 8030.As well as being electrically coupled via the contacts 809, the actuatorbeam is also mechanically anchored to anchor 808. The anchor 808 isconfigured to constrain motion of the actuator beam 807 to the left ofFIGS. 26 to 28 when the nozzle arrangement is in operation.

The TiN in the actuator beam 807 is conductive, but has a high enoughelectrical resistance that it undergoes self-heating when a current ispassed between the electrodes 809 and 8041. No current flows through thepassive beams 806, so they do not expand.

In use, the device at rest is filled with ink 8013 that defines ameniscus 803 under the influence of surface tension. The ink is retainedin the chamber 8029 by the meniscus, and will not generally leak out inthe absence of some other physical influence.

As shown in FIG. 24, to fire ink from the nozzle, a current is passedbetween the contacts 809 and 8041, passing through the actuator beam807. The self-heating of the beam 807 due to its resistance causes thebeam to expand. The dimensions and design of the actuator beam 807 meanthat the majority of the expansion in a horizontal direction withrespect to FIGS. 23 to 25. The expansion is constrained to the left bythe anchor 808, so the end of the actuator beam 807 adjacent the leverarm 8018 is impelled to the right.

The relative horizontal inflexibility of the passive beams 806 preventsthem from allowing much horizontal movement the lever arm 8018. However,the relative displacement of the attachment points of the passive beamsand actuator beam respectively to the lever arm causes a twistingmovement that causes the lever arm 8018 to move generally downwards. Themovement is effectively a pivoting or hinging motion. However, theabsence of a true pivot point means that the rotation is about a pivotregion defined by bending of the passive beams 806.

The downward movement (and slight rotation) of the lever arm 8018 isamplified by the distance of the nozzle wall 8033 from the passive beams806. The downward movement of the nozzle walls and roof causes apressure increase within the chamber 8029, causing the meniscus to bulgeas shown in FIG. 24. It will be noted that the surface tension of theink means the fluid seal 8011 is stretched by this motion withoutallowing ink to leak out.

As shown in FIG. 25, at the appropriate time, the drive current isstopped and the actuator beam 807 quickly cools and contracts. Thecontraction causes the lever arm to commence its return to the quiescentposition, which in turn causes a reduction in pressure in the chamber8029. The interplay of the momentum of the bulging ink and its inherentsurface tension, and the negative pressure caused by the upward movementof the nozzle chamber 8029 causes thinning, and ultimately snapping, ofthe bulging meniscus to define an ink drop 802 that continues upwardsuntil it contacts adjacent print media.

Immediately after the drop 802 detaches, meniscus 803 forms the concaveshape shown in FIG. 25. Surface tension causes the pressure in thechamber 8029 to remain relatively low until ink has been sucked upwardsthrough the inlet 8014, which returns the nozzle arrangement and the inkto the quiescent situation shown in FIG. 23.

Another type of printhead nozzle arrangement suitable for the presentinvention will now be described with reference to FIG. 33. Once again,for clarity and ease of description, the construction and operation of asingle nozzle arrangement 1001 will be described.

The nozzle arrangement 1001 is of a bubble forming heater elementactuator type which comprises a nozzle plate 1002 with a nozzle 1003therein, the nozzle having a nozzle rim 1004, and aperture 1005extending through the nozzle plate. The nozzle plate 1002 is plasmaetched from a silicon nitride structure which is deposited, by way ofchemical vapour deposition (CVD), over a sacrificial material which issubsequently etched.

The nozzle arrangement includes, with respect to each nozzle 1003, sidewalls 1006 on which the nozzle plate is supported, a chamber 1007defined by the walls and the nozzle plate 1002, a multi-layer substrate1008 and an inlet passage 1009 extending through the multi-layersubstrate to the far side (not shown) of the substrate. A looped,elongate heater element 1010 is suspended within the chamber 1007, sothat the element is in the form of a suspended beam. The nozzlearrangement as shown is a microelectromechanical system (MEMS)structure, which is formed by a lithographic process.

When the nozzle arrangement is in use, ink 1011 from a reservoir (notshown) enters the chamber 1007 via the inlet passage 1009, so that thechamber fills. Thereafter, the heater element 1010 is heated forsomewhat less than 1 micro second, so that the heating is in the form ofa thermal pulse. It will be appreciated that the heater element 1010 isin thermal contact with the ink 1011 in the chamber 1007 so that whenthe element is heated, this causes the generation of vapor bubbles inthe ink. Accordingly, the ink 1011 constitutes a bubble forming liquid.

The bubble 1012, once generated, causes an increase in pressure withinthe chamber 1007, which in turn causes the ejection of a drop 1016 ofthe ink 1011 through the nozzle 1003. The rim 1004 assists in directingthe drop 1016 as it is ejected, so as to minimize the chance of a dropmisdirection.

The reason that there is only one nozzle 1003 and chamber 1007 per inletpassage 1009 is so that the pressure wave generated within the chamber,on heating of the element 1010 and forming of a bubble 1012, does noteffect adjacent chambers and their corresponding nozzles.

The increase in pressure within the chamber 1007 not only pushes ink1011 out through the nozzle 1003, but also pushes some ink back throughthe inlet passage 1009. However, the inlet passage 1009 is approximately200 to 300 microns in length, and is only approximately 16 microns indiameter. Hence there is a substantial viscous drag. As a result, thepredominant effect of the pressure rise in the chamber 1007 is to forceink out through the nozzle 1003 as an ejected drop 1016, rather thanback through the inlet passage 1009.

As shown in FIG. 33, the ink drop 1016 is being ejected is shown duringits “necking phase” before the drop breaks off. At this stage, thebubble 1012 has already reached its maximum size and has then begun tocollapse towards the point of collapse 1017.

The collapsing of the bubble 1012 towards the point of collapse 1017causes some ink 1011 to be drawn from within the nozzle 1003 (from thesides 1018 of the drop), and some to be drawn from the inlet passage1009, towards the point of collapse. Most of the ink 1011 drawn in thismanner is drawn from the nozzle 1003, forming an annular neck 1019 atthe base of the drop 1016 prior to its breaking off.

The drop 1016 requires a certain amount of momentum to overcome surfacetension forces, in order to break off. As ink 1011 is drawn from thenozzle 1003 by the collapse of the bubble 1012, the diameter of the neck1019 reduces thereby reducing the amount of total surface tensionholding the drop, so that the momentum of the drop as it is ejected outof the nozzle is sufficient to allow the drop to break off.

When the drop 1016 breaks off, cavitation forces are caused as reflectedby the arrows 1020, as the bubble 1012 collapses to the point ofcollapse 1017. It will be noted that there are no solid surfaces in thevicinity of the point of collapse 1017 on which the cavitation can havean effect.

Yet another type of printhead nozzle arrangement suitable for thepresent invention will now be described with reference to FIGS. 34-36.This type typically provides an ink delivery nozzle arrangement having anozzle chamber containing ink and a thermal bend actuator connected to apaddle positioned within the chamber. The thermal actuator device isactuated so as to eject ink from the nozzle chamber. The preferredembodiment includes a particular thermal bend actuator which includes aseries of tapered portions for providing conductive heating of aconductive trace. The actuator is connected to the paddle via an armreceived through a slotted wall of the nozzle chamber. The actuator armhas a mating shape so as to mate substantially with the surfaces of theslot in the nozzle chamber wall.

Turning initially to FIGS. 34(a)-(c), there is provided schematicillustrations of the basic operation of a nozzle arrangement of thisembodiment. A nozzle chamber 501 is provided filled with ink 502 bymeans of an ink inlet channel 503 which can be etched through a wafersubstrate on which the nozzle chamber 501 rests. The nozzle chamber 501further includes an ink ejection port 504 around which an ink meniscusforms.

Inside the nozzle chamber 501 is a paddle type device 507 which isinterconnected to an actuator 508 through a slot in the wall of thenozzle chamber 501. The actuator 508 includes a heater means e.g. 509located adjacent to an end portion of a post 510. The post 510 is fixedto a substrate.

When it is desired to eject a drop from the nozzle chamber 501, asillustrated in FIG. 34(b), the heater means 509 is heated so as toundergo thermal expansion. Preferably, the heater means 509 itself orthe other portions of the actuator 508 are built from materials having ahigh bend efficiency where the bend efficiency is defined as:${{bend}\quad{efficiency}} = \frac{{{Young}'}s\quad{Modulus} \times \left( {{Coefficient}\quad{of}\quad{thermal}\quad{Expansion}} \right)}{{Density} \times {Specific}\quad{Heat}\quad{Capacity}}$

A suitable material for the heater elements is a copper nickel alloywhich can be formed so as to bend a glass material.

The heater means 509 is ideally located adjacent the end portion of thepost 510 such that the effects of activation are magnified at the paddleend 507 such that small thermal expansions near the post 510 result inlarge movements of the paddle end.

The heater means 509 and consequential paddle movement causes a generalincrease in pressure around the ink meniscus 505 which expands, asillustrated in FIG. 34(b), in a rapid manner. The heater current ispulsed and ink is ejected out of the port 504 in addition to flowing infrom the ink channel 503.

Subsequently, the paddle 507 is deactivated to again return to itsquiescent position. The deactivation causes a general reflow of the inkinto the nozzle chamber. The forward momentum of the ink outside thenozzle rim and the corresponding backflow results in a general neckingand breaking off of the drop 512 which proceeds to the print media. Thecollapsed meniscus 505 results in a general sucking of ink into thenozzle chamber 502 via the ink flow channel 503. In time, the nozzlechamber 501 is refilled such that the position in FIG. 34(a) is againreached and the nozzle chamber is subsequently ready for the ejection ofanother drop of ink.

FIG. 35 illustrates a side perspective view of the nozzle arrangement.FIG. 36 illustrates sectional view through an array of nozzlearrangement of FIG. 35. In these figures, the numbering of elementspreviously introduced has been retained.

Firstly, the actuator 508 includes a series of tapered actuator unitse.g. 515 which comprise an upper glass portion (amorphous silicondioxide) 516 formed on top of a titanium nitride layer 517.Alternatively a copper nickel alloy layer (hereinafter calledcupronickel) can be utilized which will have a higher bend efficiency.

The titanium nitride layer 517 is in a tapered form and, as such,resistive heating takes place near an end portion of the post 510.Adjacent titanium nitride/glass portions 515 are interconnected at ablock portion 519 which also provides a mechanical structural supportfor the actuator 508.

The heater means 509 ideally includes a plurality of the taperedactuator unit 515 which are elongate and spaced apart such that, uponheating, the bending force exhibited along the axis of the actuator 508is maximized. Slots are defined between adjacent tapered units 515 andallow for slight differential operation of each actuator 508 withrespect to adjacent actuators 508.

The block portion 519 is interconnected to an arm 520. The arm 520 is inturn connected to the paddle 507 inside the nozzle chamber 501 by meansof a slot e.g. 522 formed in the side of the nozzle chamber 501. Theslot 522 is designed generally to mate with the surfaces of the arm 520so as to minimize opportunities for the outflow of ink around the arm520. The ink is held generally within the nozzle chamber 501 via surfacetension effects around the slot 522.

When it is desired to actuate the arm 520, a conductive current ispassed through the titanium nitride layer 517 within the block portion519 connecting to a lower CMOS layer 506 which provides the necessarypower and control circuitry for the nozzle arrangement. The conductivecurrent results in heating of the nitride layer 517 adjacent to the post510 which results in a general upward bending of the arm 20 andconsequential ejection of ink out of the nozzle 504. The ejected drop isprinted on a page in the usual manner for an inkjet printer aspreviously described.

An array of nozzle arrangements can be formed so as to create a singleprinthead. For example, in FIG. 36 there is illustrated a partlysectioned various array view which comprises multiple ink ejectionnozzle arrangements laid out in interleaved lines so as to form aprinthead array. Of course, different types of arrays can be formulatedincluding fill color arrays etc.

The construction of the printhead system described can proceed utilizingstandard MEMS techniques through suitable modification of the steps asset out in U.S. Pat. No. 6,243,113 entitled “Image Creation Method andApparatus (IJ 41)” to the present applicant, the contents of which arefully incorporated by cross reference.

The integrated circuits 74 may be arranged to have between 5000 to100,000 of the above described ink delivery nozzles arranged along itssurface, depending upon the length of the integrated circuits and thedesired printing properties required. For example, for narrow media itmay be possible to only require 5000 nozzles arranged along the surfaceof the printhead assembly to achieve a desired printing result, whereasfor wider media a minimum of 10,000, 20,000 or 50,000 nozzles may needto be provided along the length of the printhead assembly to achieve thedesired printing result. For full colour photo quality images on A4 orUS letter sized media at or around 1600 dpi, the integrated circuits 74may have 13824 nozzles per color. Therefore, in the case where theprinthead assembly 22 is capable of printing in 4 colours (C, M, Y, K),the integrated circuits 74 may have around 53396 nozzles disposed alongthe surface thereof. Further, in a case where the printhead assembly 22is capable of printing 6 printing fluids (C, M, Y, K, IR and a fixative)this may result in 82944 nozzles being provided on the surface of theintegrated circuits 74. In all such arrangements, the electronicssupporting each nozzle is the same.

The manner in which the individual ink delivery nozzle arrangements maybe controlled within the printhead assembly 22 will now be describedwith reference to FIGS. 37-40.

FIG. 37 shows an overview of the integrated circuit 74 and itsconnections to the SoPEC device (discussed above) provided within thecontrol electronics of the print engine 1. As discussed above,integrated circuit 74 includes a nozzle core array 901 containing therepeated logic to fire each nozzle, and nozzle control logic 902 togenerate the timing signals to fire the nozzles. The nozzle controllogic 902 receives data from the SoPEC device via a high-speed link.

The nozzle control logic 902 is configured to send serial data to thenozzle array core for printing, via a link 907, which may be in the formof an electrical connector. Status and other operational informationabout the nozzle array core 901 is communicated back to the nozzlecontrol logic 902 via another link 908, which may be also provided onthe electrical connector.

The nozzle array core 901 is shown in more detail in FIGS. 38 and 39. InFIG. 38, it will be seen that the nozzle array core 901 comprises anarray of nozzle columns 911. The array includes a fire/select shiftregister 912 and up to 6 color channels, each of which is represented bya corresponding dot shift register 913.

As shown in FIG. 39, the fire/select shift register 912 includes forwardpath fire shift register 930, a reverse path fire shift register 931 anda select shift register 932. Each dot shift register 913 includes an odddot shift register 933 and an even dot shift register 934. The odd andeven dot shift registers 933 and 934 are connected at one end such thatdata is clocked through the odd shift register 933 in one direction,then through the even shift register 934 in the reverse direction. Theoutput of all but the final even dot shift register is fed to one inputof a multiplexer 935. This input of the multiplexer is selected by asignal (corescan) during post-production testing. In normal operation,the corescan signal selects dot data input Dot[x] supplied to the otherinput of the multiplexer 935. This causes Dot[x] for each color to besupplied to the respective dot shift registers 913.

A single column N will now be described with reference to FIG. 40. Inthe embodiment shown, the column N includes 12 data values, comprisingan odd data value 936 and an even data value 937 for each of the six dotshift registers. Column N also includes an odd fire value 938 from theforward fire shift register 930 and an even fire value 939 from thereverse fire shift register 931, which are supplied as inputs to amultiplexer 940. The output of the multiplexer 940 is controlled by theselect value 941 in the select shift register 932. When the select valueis zero, the odd fire value is output, and when the select value is one,the even fire value is output.

Each of the odd and even data values 936 and 937 is provided as an inputto corresponding odd and even dot latches 942 and 943 respectively.

Each dot latch and its associated data value form a unit cell, such asunit cell 944. A unit cell is shown in more detail in FIG. 40. The dotlatch 942 is a D-type flip-flop that accepts the output of the datavalue 936, which is held by a D-type flip-flop 944 forming an element ofthe odd dot shift register 933. The data input to the flip-flop 944 isprovided from the output of a previous element in the odd dot shiftregister (unless the element under consideration is the first element inthe shift register, in which case its input is the Dot[x] value). Datais clocked from the output of flip-flop 944 into latch 942 upon receiptof a negative pulse provided on LsyncL.

The output of latch 942 is provided as one of the inputs to athree-input AND gate 945. Other inputs to the AND gate 945 are the Frsignal (from the output of multiplexer 940) and a pulse profile signalPr. The firing time of a nozzle is controlled by the pulse profilesignal Pr, and can be, for example, lengthened to take into account alow voltage condition that arises due to low power supply (in aremovable power supply embodiment). This is to ensure that a relativelyconsistent amount of ink is efficiently ejected from each nozzle as itis fired. In the embodiment described, the profile signal Pr is the samefor each dot shift register, which provides a balance betweencomplexity, cost and performance. However, in other embodiments, the Prsignal can be applied globally (ie, is the same for all nozzles), or canbe individually tailored to each unit cell or even to each nozzle.

Once the data is loaded into the latch 942, the fire enable Fr and pulseprofile Pr signals are applied to the AND gate 945, combining to thetrigger the nozzle to eject a dot of ink for each latch 942 thatcontains a logic 1.

The signals for each nozzle channel are summarized in the followingtable: Name Direction Description D Input Input dot pattern to shiftregister bit Q Output Output dot pattern from shift register bit SrClkInput Shift register clock in - d is captured on rising edge of thisclock LsyncL Input Fire enable - needs to be asserted for nozzle to firePr Input Profile - needs to be asserted for nozzle to fire

As shown in FIG. 40, the fire signals Fr are routed on a diagonal, toenable firing of one color in the current column, the next color in thefollowing column, and so on. This averages the current demand byspreading it over 6 columns in time-delayed fashion.

The dot latches and the latches forming the various shift registers arefully static in this embodiment, and are CMOS-based. The design andconstruction of latches is well known to those skilled in the art ofintegrated circuit engineering and design, and so will not be describedin detail in this document.

The nozzle speed may be as much as 20 kHz for the printer unit 2 capableof printing at about 60 ppm, and even more for higher speeds. At thisrange of nozzle speeds the amount of ink than can be ejected by theentire printhead assembly 22 is at least 50 million drops per second.However, as the number of nozzles is increased to provide forhigher-speed and higher-quality printing at least 100 million drops persecond, preferably at least 500 million drops per second and morepreferably at least 1 billion drops per second may be delivered. At suchspeeds, the drops of ink are ejected by the nozzles with a maximum dropejection energy of about 250 nanojoules per drop.

Consequently, in order to accommodate printing at these speeds, thecontrol electronics must be able to determine whether a nozzle is toeject a drop of ink at an equivalent rate. In this regard, in someinstances the control electronics must be able to determine whether anozzle ejects a drop of ink at a rate of at least 50 milliondeterminations per second. This may increase to at least 100 milliondeterminations per second or at least 500 million determinations persecond, and in many cases at least 1 billion determinations per secondfor the higher-speed, higher-quality printing applications.

For the printer unit 2 of the present invention, the above-describedranges of the number of nozzles provided on the printhead assembly 22together with the nozzle firing speeds and print speeds results in anarea print speed of at least 50 cm² per second, and depending on theprinting speed, at least 100 cm² per second, preferably at least 200 cm²per second, and more preferably at least 500 cm² per second at thehigher-speeds. Such an arrangement provides a printer unit 2 that iscapable of printing an area of media at speeds not previously attainablewith conventional printer units.

Maintenance Assembly

The maintenance assembly 23 is shown in detail in FIGS. 41-44, and aspreviously shown in FIG. 8, it is mounted between the posts 26 of themain body 20, so as to be positioned adjacent the printhead assembly 22.

The maintenance assembly 23 generally consists of a maintenance chassis88 which receives the various components of the assembly therein. Themaintenance chassis 88 is in the form of an open ended channel having apair of upwardly extending tongue portions 89 at its ends which areshaped to fit over the posts 26 of the main body 20 and engage with theretaining projections provided thereon to secure the maintenanceassembly 23 in position. The maintenance chassis 88 is made from asuitable metal material, having rigidity and resilience, such as apressed steel plate.

The base of the maintenance chassis 88 is shown more clearly in FIG. 43and includes a centrally located removed portion 90, window portions 92and spring arms 91 extending from either side of the window portions 92.The integral spring arms 91 are angled internally of the chassis 88 andformed by pressing the sheet metal of the chassis. Of course the springarms 91 could equally be a separate insert placed into the open channelof the chassis 88.

A rigid insert 93 is provided to fit within the chassis 88 to provideadded rigidity to the maintenance assembly 23. A catch element 94projects from the base of the rigid insert and extends into thecentrally located removed portion 90 of the chassis 88 when the rigidinsert 93 is located within the chassis 88. The catch element 94 isprovided to move the maintenance assembly between a capped and anuncapped state, as will be described below. A lower maintenance molding95 is located within the insert 93 and retained within the insert viaengagement of a number of lugs 96 formed along the sides of the lowermaintenance molding 95 with corresponding slots 97 provided along thesides of the insert 93. The lower maintenance molding 95 is made from asuitable plastic material and forms a body having closed ends and anopen top. The ends of the lower maintenance molding 93 are provided withair vents 98. Air from the vents 98 flows through filters 181 toventilate the maintenance assembly.

Two pin elements 99 extend from the base of the lower maintenancemolding 95. The pin elements 99 are connected to the base via a flexibleweb, such as rubber, to allow multi-directional relative movement of thepin elements 99 with respect to the base of the lower maintenancemolding. The pin elements 99 pass through two circular openings 100 inthe base of the rigid insert 93 and into the window portions 92 of themaintenance chassis 88.

A retainer insert 101 is supported on the pin elements 99 within thelower maintenance molding 95. The retainer insert 101 is coated steeland provides rigid support for the strips of absorbent media 102retained therein. The absorbent media 102 is a generally an invertedT-shaped assembly of separate portions—a thin vertical portion whichextends upwardly from between two substantially horizontal portions. Theabsorbent media 102 may be made from any type of material capable ofabsorbing and retaining ink such as urethane foam or the like.

A microfibre fabric 103 fits over the thin vertical portion, around thetwo horizontal portions, and then attaches to the retainer insert 101 toretain the absorbent media 102. The microfibre fabric 103 draws into theabsorbent media 102.

An upper maintenance molding 104 fits over the lower maintenance molding95 to enclose the microfibre fabric 103, absorbent media 102 andretainer insert 101 therebetween. The upper maintenance molding 104 isattached along its bottom surface to the surface of the lowermaintenance molding 95 via an appropriate adhesive. An upwardlyprojecting rim portion 105 extends beyond the thin vertical portion ofthe absorbent media 102 covered with microfibre fabric 103. The rimportion 105 defines an open perimeter seal for sealing the nozzles ofthe printhead assembly 22 when the upper maintenance molding 104 isbrought into capping contact with the printhead assembly.

In this arrangement, the upper maintenance molding 104, microfibrefabric 103, absorbent media 102, retainer insert 101, lower maintenancemolding 95 and the rigid insert 93 form a capping unit which is adaptedto fit within the maintenance chassis 88 and is supported on the springarms thereof. Within this unit, the microfibre fabric 103, absorbentmedia 102 and the retainer insert 101 form a sub-unit supported on thepin elements 99 and movable within the space defined by the lowermaintenance molding 95 and the upper maintenance molding 104.

As shown in FIG. 41, the capping unit is held in place with a retainerelement 106 that fits over the upper maintenance molding 104 and securesto the chassis 88. The retainer element 106 is essentially in the formof an open ended channel having a slot 107 formed along the uppersurface thereof, through which the rim portion 105 of the uppermaintenance molding 104 can protrude and cappingly engage with theprinthead assembly 22. The upper surface of the retainer element 106 iscurved and acts as a media guide during printing.

When assembled in this manner, the components of the maintenanceassembly 23 are contained within the retainer element 106 and thechassis 88, such that both the upper maintenance molding 104 can movewith respect to the retainer element 106 to cap the printhead assembly22, and the microfibre fabric 103 and absorbent media 102 can move withrespect to the upper maintenance molding to contact and wipe the surfaceof the nozzles of the printhead assembly 22.

Upon assembly and attachment of the maintenance assembly 23 to the posts26 of the main body 20, the catch element 94 of the rigid insert extendsfrom the central removed portion 90 of the chassis 88. Due to the actionof the spring arms 91, the maintenance unit 23 (as previously defined)is raised from the base of the chassis 88 such that the rim portion 105of the upper maintenance molding 104 extends through the slot 107 of theretainer element 106 and is in capping contact with the printheadassembly 22. This state is shown in FIG. 44 and is referred to as thecapping state, whereby the nozzles of the printhead are sealed in analmost closed environment within the rim portion 105 and are less likelyto dry out and clog with ink. The environment is almost closed and notfully closed, so that the maintenance assembly is not prevented frommoving to the uncapped state because of a mild vacuum created within therim 105.

To remove any paper dust or other particulate matter present in thevicinity of the nozzles of the printhead assembly 22, the surface of theprinthead may be wiped by the microfibre fabric 103. To perform this, awiper actuator present in the cradle unit extends into the windowportions 92 of the chassis 88 and contacts the pin elements 99 providedin the base of the lower maintenance molding 95. Any upward forceprovided by the wiper actuator on the pins 99 causes them to projectfurther against the retainer insert 101, thereby causing the verticalportion of the absorbent media 102, which is coated with the microfibrefabric 103, to extend into and beyond the rim portion 105 of the uppermaintenance molding 104, until it contacts the surface of the printheadassembly 22 proximal the nozzles. The presence of the microfibre fabric103 ensures that contact is minimised and attracts any ink or moisturepresent on the surface of the printhead assembly 22 to be retainedwithin the absorbent media 102. As the pins 99 are free to move in anydirection, any lateral motion of the wiper actuator will cause themicrofibre fabric 103 to move laterally across the surface of thenozzles hence performing a wiping or cleaning function. Removal of thewiper actuator will then cause the arrangement to return to a positionwhereby the microfibre fabric 103 and the absorbent media 102 are belowthe surface of the rim portion 105.

In order to perform printing, the maintenance assembly 23 must be movedfrom the capping state to a printing state. This is achieved by amaintenance actuator gripping the catch element 94 projecting throughthe central removed portion 90 of the chassis 88 and applying a downwardforce thereto. This downward force causes the rigid insert 93 to moveagainst the spring arms 91 of the chassis 88, towards the base of thechassis. This movement causes the upper rim portion 105 of the uppercapping molding 104 to retract into the slot 107 formed in the retainerelement 106 such that it is flush with the outer surface of the retainerelement 106 and does not protrude therefrom. It will be appreciated thatthe retainer element 106 does not move and is fixed in position. Thiscreates a gap between the retainer element 106 and the printheadassembly 22 through which the media can pass for printing. In theprinting or uncapped state, the retainer element 106 acts as a mediaguide and the media contacts the retainer element and is supported onthe surface of the retainer element 106 as it passes the printheadassembly for printing.

Cradle Unit

The cradle unit 12 is shown in relation to FIGS. 6 and 7 and generallyconsists of a main body 13 which defines an opening 14 for receiving thecartridge unit 10, and a cover assembly 11 adapted to close the openingto secure the cartridge unit 10 in place within the cradle unit 12.

The main body 13 of the cradle unit 12 includes a frame structure 110 asshown in FIGS. 45A and 45B. The frame structure 110 generally comprisestwo end plates 111 and a base plate 112 connecting each of the endplates 111. A drive roller 113 and an exit roller 114 are mountedbetween the end plates 111 at opposing ends thereof, such that when thecartridge unit 10 is retained within the main body 13, it sets betweenthe drive roller 113 and exit roller 114. The drive roller 113 and theexit roller 114 are each driven by a brushless DC motor 115 which ismounted to one of the end plates 111 and drives each of the drive andexit rollers via a drive mechanism 116, such as a drive belt. Such asystem ensures that both the drive roller 113 and the exit roller 114are driven at the same speed to ensure a smooth and consistent passageof the media through the print engine 1 and past the printhead assembly22 of the cartridge unit 10.

A maintenance drive assembly 117 is mounted to the other end plate 111,opposite the DC motor 107. The maintenance drive assembly 117 comprisesa motor 118 which is operatively connected to a maintenance gear 119 anda wiper gear 120. The maintenance gear 119 is in turn connected to amaintenance actuator 121 which is in the form of a rod having a hookedend that extends a distance within the base plate 112. The hooked end ofthe maintenance actuator 121 is shaped to be received within the catchelement 94 of the maintenance assembly 23 so as to raise/lower the upperrim portion 105 between the capping state and the printing state. Thewiper gear 120 is similarly connected to a wiper actuator 122 in theform of a rod having a pair of projections extending therefrom. Thewiper actuator 122 similarly extends within the base plate 112, and theprojections are positioned along the wiper actuator 122 so that they arealigned with the window portions 92 formed in the base of themaintenance chassis 88 so as to contact the pin elements 99 of themaintenance assembly 23.

The maintenance drive assembly 117 is shown in isolation in FIGS. 46Aand 46B. As the motor 118 is bi-directional, operation of the motor inone direction will cause the wiper gear 120 to move in acounter-clockwise direction as shown in FIG. 46A. The wiper gear 120,has a raised portion 123 formed on the surface thereof which comes intocontact with an arm 124 of the wiper actuator as the wiper gear 120rotates. As the raised portion 123 contacts the arm 124, the wiperactuator 122 pivots such that the projections formed thereon move in anupward direction through the window portions 92 in the maintenancechassis 88 and against the pin elements 99, thereby bring the microfibre fabric 103 against the surface of the printhead assembly. Furtherrotation of the wiper gear 120 will result in the arm 124 returning toits neutral position. Lateral movement can be applied to the wiperactuator 122 due to the presence of an additional angled raised portion125 formed on the wiper gear 120 upon which the arm 124 rides causes theentire wiper actuator to move laterally against the returning spring126. A sensor element 127 is provided to sense the position of the wiperactuator such that the state of the printhead can be readily determined.

In order to control the capping state of the printhead assembly 22, themotor 118 is reversed resulting in the wiper gear 120 moving in aclockwise direction as shown in FIG. 46A and a counter-clockwisedirection as shown in FIG. 46B. Rotation of the wiper gear 120 in thisdirection ensures that the wiper actuator pivots in a downward directionaway from the maintenance assembly 23. However as shown more clearly inFIG. 46B, this rotation causes a flipper gear 128 provided on the innersurface of the wiper gear 120 to engage with the maintenance gear 119and in turn cause the maintenance gear 119 to rotate in a counterclockwise direction (as shown in FIG. 46B). Similarly, a projection 129formed on the inner surface of the maintenance gear 119 contacts a pivotarm 130 of the maintenance actuator 121, thereby causing the hooked endof the maintenance actuator to move in a downward direction, which inturn grips the catch element 94 of the maintenance assembly 23 causingthe upper rim portion 105 to retract and assume a printing state.Similarly, the sensor element 127 can sense the position of themaintenance actuator to control operation of the motor 118, and hencethe desired state of the printhead.

Referring again to FIGS. 45A and 45B, a pair of cartridge unit guides131 are attached to the end plates 111 to aid in receiving and guidingthe cartridge unit 10 into the cradle unit 12. The guides 131 are angledto receive a surface of the cartridge unit 10 such that the cartridgeunit 10 is orientated correctly with respect to the cradle unit 12.

The control electronics for controlling the operation of the printengine and the ICs 50 of the printhead assembly 22 is provided on aprinted circuit board (PCB) 132. As shown in FIG. 45A, one face of thePCB 132 contains the SoPEC devices 133 and related componentry 134 forreceiving and distributing the data and power received from externalsources, whilst the other face of the PCB includes rows of electricalcontacts 135 along a lower edge thereof which provides a means fortransmitting the power and data signals to the corresponding electricalcontacts on the flex PCB 79 for controlling the nozzles of the printheadassembly 22.

As shown in isolation in FIG. 47, the PCB 132 forms part of a PCBassembly 140, and is mounted between two arms 136, with each of the armshaving a claw portion 137 to receive and retain the PCB 132 in position.As shown in FIG. 48, each of the arms 136 has a groove 141 formed in theupper portion thereof for receiving a hook portion of a tension spring142, the purpose of which will be described below.

In order to provide stability to the PCB 132 as it is mounted betweenthe two arms 136, a support bar 138 is secured to the arms 136 and thePCB along the bottom edge of the PCB 132, on the face that contains theSoPEC devices 133 and the related componentry 134. The support bar 138has a plurality of star wheels 139 mounted along its lower surface. Thestar wheels are spring loaded such that they can move relative to thelower surface of the support bar to grip with a surface of the exitroller 114 when the PCB assembly 140 is mounted to the end plates 111,as shown in FIG. 45A.

A heatshield 143 is attached to the PCB 132, as shown in FIG. 49A suchthat it substantially covers the SoPEC devices 133 and protects theSoPEC devices from any EMI that may be within the vicinity of theprinter unit 2. The heatshield 143 also has a latch mechanism 144provided therein which mates with a clip provided on the cover assembly11 to secure the cover assembly in a closed position as shown in FIG.49A.

The PCB assembly 140 is pivotally mounted to the end plates 111 at pivotpoints 141 provided at the bottom of the arms 136. In this arrangement,the PCB assembly 140 is able to swing about its pivot points 141 betweenan open position, wherein the electrical contacts 135 are remote fromthe electrical contacts of the flex PCB 79 and the cartridge unit 10 canbe readily removed from the cradle unit 12, and a closed position, wherethe electrical contacts 135 are in operational contact with theelectrical contacts provided on the flex PCB 79 to transmit control dataand power to facilitate printing from the nozzles of the printheadassembly 22.

As shown in FIG. 49B, an idle roller assembly 145 is secured to the endplates 111 at the rear of the cradle unit 12 and includes a plurality ofroller wheels 146 which are positioned to contact the surface of thedrive roller 113 and rotate therewith. The idle roller assembly 145ensures that any media that is presented to the print engine 1 from thepicker mechanism 9 of the printer unit 2, is gripped between the driveroller 113 and the roller wheels 146 of the idle roller assembly 1145for transport past the printhead assembly 22 of the cartridge unit 10for printing.

The cover assembly 11, is shown in its closed position in FIGS. 49A and49B, and is pivotally attached to the end plates 111 at an upper rearportion thereof A pair of attachment plates 147 extend from the coverassembly 11 for attaching the cover assembly to the end plates 111 via apin 148. The attachment plates 147 extend beyond the pin 148 and have ahole formed therein into which is received the free end of the tensionspring 142 as discussed previously in relation to FIG. 48.

When the cover assembly 11 is in the closed position, as shown in FIG.49B, the spring is in full tension which in turn causes the PCB assembly40 to pivot towards the closed position, as shown in cross-section inFIG. 50A. In this position, the electrical contacts 135 of the PCB 132are in operational contact with the corresponding electrical contacts ofthe flex PCB 79 of the printhead assembly 22 such that power and datasignals can be transferred therebetween.

When the cover assembly is moved to its open position, as shown in FIG.49C, the attachment plates 147 pivot towards the front of the cradleassembly thereby relieving tension in the spring 142 and causing thespring to become slack. This in turn, allows the PCB assembly to pivotaway into an open position as shown in FIG. 50B. In this position, theelectrical contacts 135 of the PCB 132 move away from contacting thecorresponding contacts of the flex PCB 79 of the printhead assembly 22,to thereby enable the cartridge unit 10 to be removed from the cradleunit 12.

In this regard, the act of opening/closing the cover assembly 11 alsoperforms the function of disengaging/engaging electrical communicationbetween the cartridge unit 10 and the cradle unit 12.

Referring again to FIGS. 49A-49C, the cover assembly 11 includes anumber of docking ports 149 formed in the upper surface thereof. In theembodiment shown there are five docking ports 149 provided, with eachdocking port corresponding to one of the ink storage modules 45. Eachdocking port 149 has an upwardly projecting lip portion which is shapedto receive an ink refill unit for supplying refill ink to the inkstorage modules 45. As more clearly shown in FIG. 49C, each docking port149 has a large, substantially circular opening 151 and two smallcircular openings 152 provided therein, which enable the delivery of inkbetween the ink refill unit and the cartridge unit 10 to occur in themanner as described below.

Four T-shaped openings 182 are positioned at the corners of each dockingportion 149 to receive the bag constrictor actuators on the refill.These were briefly discussed above in relation to the ink storagemodules 45 and are described in more detail below.

Refill Unit

FIGS. 51A-51C show the ink refill unit 155 for supplying refill ink tothe cartridge unit 10. The ink refill unit 155 is provided as a unitcomprising a base assembly 156 which houses internal ink refillingcomponents and a cover 157 which fits over the base assembly 156. Thebase assembly and cover may be moulded from a plastics material and thebase assembly 156 may be moulded as a single piece or in sections.

The underside of the base assembly 156 is shown in more detail in FIG.51B and includes a ridge portion 160 that projects therefrom and whichmates with docking port 149 formed in the cover assembly 11, to retainthe ink refill unit in docking position. A substantially cylindrical inkoutlet 158 also projects from the underside of the base assembly fordelivering ink into the cartridge unit 10. A two valve actuating pins159 also project from the underside of the base assembly 156 foractuating the inlet and outlet valves of the ink storage modules 45respectively. In the embodiment shown, the two valve actuating pins 159have a tri star cross section for good uni-directional bendingresistance and buckling strength. A QA chip 161 is also provided toproject from the underside of the base assembly 156 and has a pluralityof QA chip contacts 162 exposed thereon which are read by a QA chipreader provided in the cover assembly 11 when the ink refill unit 155 isdocked therewith.

A constrictor actuator 190 projects from adjacent each corner of thebase assembly 156. The constrictor actuators 190 are slightly arcuateand rounded at their ends. The constrictor apertures 60 (see FIG. 14) inthe top 42 of the cartridge unit 10, are correspondingly arcuate. Therounded ends and arcuate cross section allow the user to easily alignone constrictor actuator 190 with its corresponding aperture 60, and thecurved surfaces intuitively guide the other constrictor actuators 190into alignment with their respective apertures 60. This helps to dockthe refill unit with the interface 61 quickly and with minimal finepositioning by the user. As best shown in FIG. 51B, each constrictoractuator 190 has a buttress reinforcement 191. This gives theconstrictor actuators 190 a high bending strength in order to withstandlarge lateral forces in the event that users apply excessive force whenaligning the refill unit with the docking port.

As described above with reference to FIG. 12, the constrictor actuators190 actuate the bag constrictor 43 of the ink storage module 45.

The base assembly 156 also has a filling port 192. The bag 163 receivesits initial charge of ink through this port which is then sealed with aplastic sealing ball 193.

Referring to the exploded view of FIG. 51C, an ink bag 163 is sealed tothe inner surface of the base assembly 156 for storing the refill inktherein, and is made from a deformable material which allows the ink bag163 to expand/collapse as ink is supplied to/removed from the ink refillunit 155. An ink delivery needle 164 extends into the space providedbetween the bag 163 and the base assembly 156 and provides a passage forink to flow to the outlet 158. The end of the ink delivery needle 164extends into the cylindrical outlet 158, and is surrounded by a sealring 165 which is spring loaded via a compression spring 166 within theopen end of the cylindrical outlet 158. When the ink refill unit 155 isnot docked with the cartridge unit 10, the delivery needle is protectedby the seal ring 165. As a further precaution, a plastic cap 187 is slidover the outlet and held in place by a slight interference fit.

An ink level indicator 167 is also provided within the cover 157 of theink refill unit 155. The ink level indicator 167 comprises a flexiblestrip having an indication portion 168, such as a coloured section. Thestrip is attached to the upper surface of the deformable ink bag 163 atits ends and to the underside of the cover 157 at its centre, so thatwhen the ink supply within the bag 163 is exhausted, i.e., the bag issubstantially empty, the indication portion 168 aligns itself with atransparent window 169 provided in the top surface of the cover 157. Inthis regard, at any other time, i.e., when the bag is other thansubstantially empty, the indication portion is hidden from view.

As the ink dispenses, the nature of the ink bag material causes it todeform and collapse in a non-uniform manner. Each of the edges of theupper surface of the bag are unlikely to collapse at the same rate. Assuch, the length of the ink level indicator 167 is ensures that theindication portion 168 only aligns with the window 169 in the cover 157once all of the edges of the deformable bag's upper surface have fullycollapsed. The ink level indicator strip 282 is initially in a foldedstate with the indication portion 168 being located on the strip 282 soas to be hidden from the window 169 when the bag 163 is full. The strip167 is attached at either end to opposite edges of the bag's uppersurface. A point (not shown) intermediate the ends is secured beneaththe transparent window 169. When the bag 46 fully collapses the strip167 lengthens and unfolds. This brings the previously hidden indicationportion 168 into view through the window 169. The use of the ink levelindicator 167 means that the one refill unit 155 can be used formultiple refill operations if the refill unit is not fully exhausted.This may occur when the amount of ink necessary for refilling thecorresponding ink storage module 45 of the cartridge unit 10 in oneoperation is less than the capacity of the refill unit.

The cover 157 fits over a portion of the base assembly 156 to enclosethe ink bag 163 and ink level indicator 167. Likewise, U-shaped dockingclasp 183 fits over the cover 157 such that its legs extend beyond thebase assembly 156 to engage the cartridge unit 10 when docked. Clips 170on opposing legs of the clasp 183 snap lock onto the sides of thecartridge unit 10. This holds the refill unit 155 substantially fixedrelative the cover assembly 11 for reliable and efficient transfer ofink.

An opposing pair of leaf springs 184 extend from inside each leg of theU-shaped clasp to press against the sides of the cover 157. Adjacenteach leaf spring is a pivot 185 designed to engage a fulcrum ledge 186on the side of the cover 157. This pushes the legs outwardly, however asthe pivot 185 engages the fulcrum 186, the clips are levered inwardly tomaintain engagement with the cartridge unit 10.

A label panel 188 is fixed to the outer surface of the clasp 183. Thelabel panel 188 can display trademark and other information. It may alsobe coloured to match the ink within the refill. The label panel 188 alsohas finger grip pads 189 on each leg. The finger grip pads 189 arepositioned so that finger pressure at these points will overcome theforce of the leaf springs 184 to lever the clips 170 out of engagementwith cartridge unit 10. The refill unit 155 may then be pulled off thedocking port 149 of the cover assembly 11.

FIG. 52 shows the refill unit 155 docked directly with one of theinterfaces 61 of the ink storage module assembly 11 of the cartridgeunit 10. The cover assembly 11 and remainder of the cradle unit havebeen removed for clarity. The refill unit 155 is shaped, or ‘keyed’,such that it can only be received within the docking port 149 in oneparticular orientation. The ends of each leg of the U-shapes clasp 183are significantly different widths so that the user is less likelyattempt to dock the unit 155 back-to-front. The cylindrical ink outlet158 is offset from the lateral centre line to also guard againstback-to-front docking of the refill unit 155. As previously discussed,the base of the docking port 149 has a large circular opening 151, intowhich is received the cylindrical ink outlet 158, and two smalleropenings 152, into which the valve actuators 159 are received. The crosssections of each of these interacting elements are shaped so that onlythe correctly coloured ink refill unit, in the correct orientation, canbe used to refill each particular ink storage module 45. For example,the two tri star cross sections of the valve actuators 159 can each berotated to give a large number of combinations that will only mate withcorresponding tri star apertures, each with a matching rotationalorientation.

A QA chip reader 172 is also provided in the base of the docking port149 for mating with the QA chip contacts 162 of the QA chip 161 of therefill unit 155 and reading and receiving information stored thereon.Such information may include the storage capacity of the refill unit 155(e.g., about 30 to about 50 ml), the colour of the ink contained withinthe refill unit 155, and the source of the ink contained within the inkrefill unit 155. The information can be readily transferred to thecontrol circuitry of the cradle unit 12 when the refill unit 155 isdocked into position within the docking port 149. For example, thecontrol circuitry of the cradle unit 12 is able to determine which ofthe ink storage modules 45 require refilling and whether the refill unit155 contains the correct type/colour and amount of ink to facilitaterefilling.

As shown more clearly in FIG. 53, the valve insert 49 of each of the inkstorage modules 45 (see FIG. 10) is arranged such that the ink inlet 15is aligned with the large circular opening 151 formed in the dockingport 149, and the ink inlet and outlet valves 16 and 18 respectively(obscured by the tri star openings 152), are aligned with the smallercircular openings 252. As the ink refill unit 155 is brought intoposition within the docking port 149, the ink outlet 158 of the refillunit 155 contacts the ink inlet 15 of the ink storage assembly 45, andthe valve actuator pins 159 contact each of the ink inlet valve 16 andink outlet valve 18.

In this position, the ink delivery needle 164 penetrates the ink inlet15 of the valve insert 49 as the spring loaded seal ring 165 retractswithin the cylindrical ink outlet 158 to form a tight seal around thesurface of the ink inlet 15. The seal ring 165 is able to ‘ride’ up theink delivery needle 164 and is loaded such that upon removal of therefill unit 155 from the docking port 149, the seal ring is returned toits protection position via action of a seal spring 166.

As discussed previously, the ink retained within ink bag 46 of the inkstorage module 45 is in a constant state of negative pressure due to thespring element 54 applying a constant expansion force to the ink bag 46.This produces a negative or back pressure in the ink, thereby preventingink from leaking from the nozzles of the printhead assembly 22. Thisback pressure also provides a simple means for extracting the refill inkfrom the refill unit 155 when the refill unit is docked into position.Due to a pressure gradient between the ink bag of the refill unit 155(which is at atmospheric pressure) and the ink bag of the ink storagemodule 45, when the ink delivery needle 164 penetrates the ink inlet 15,the refill ink simply flows from the refill init 155 into the ink bag 46of the ink storage module 45.

In order to alternate between a refilling operation and a printingoperation and to maintain the ink in the printhead assembly 22 in aconstant state of back pressure such that ink does not leak from thenozzles during refilling, valves 16 and 18 are provided in the valveinsert as discussed above. Both valves are controlled by the valveactuator pins 159 when the refill unit is docked into position with thedocking port 149. The manner in which the valves are controlled is shownwith reference to FIGS. 54A-54D.

FIGS. 54A and 54B show different cross-sectional views respectivelyalong lines A-A and B-B in FIG. 53 illustrating a state of the valvearrangement before refilling, and FIGS. 54C and 54D respectively showthe views of FIGS. 54A and 54B illustrating a state of the valvearrangement during refilling.

Prior to refilling, as shown in FIGS. 54A and 54B, the ink inlet valve16 is in a closed position, thereby preventing the passage of ink or airfrom entering the ink inlet 15 and making its way into the ink bag 46.This is shown in FIG. 54B, whereby any ink present in the passagebetween the ink inlet 15 and the ink inlet valve 16 remains in thisspace. An o-ring seal is provided at the ink inlet 15 to maintain an airtight seal around the ink delivery needle 164 of the refill unit 155. Inthis state, the ink outlet valve 18 is in an open position therebyproviding a passage for ink to flow out the ink outlet 52, down the inkdownpipe 30 and to the printhead assembly 22. As discussed, the springelement 54 establishes a state of back pressure within the ink bag 46,and the printhead 22 draws the ink from the ink bag 46 against this backpressure during printing.

During refilling, as shown in FIGS. 54C and 54D, the ink refill unit 155is docked into the docking port 149 such that the ink outlet 158 engageswith the ink inlet 15 of the valve insert 49 and the valve actuator pins159 come into engagement with the valves 16 and 18. As shown in FIG.54C, contact of the valve actuator pin with the ink outlet valve 18causes the valve 18 to be depressed and close, thereby preventingfurther ink flow from the ink outlet 52 to the printhead assembly 22. Inthis regard, ink present in the passage from the closed ink outlet valve18 to the printhead assembly 22 remains stationary until the ink outletvalve 18 opens.

As shown more clearly in FIG. 54D, when the valve actuator pin 159contacts the ink inlet valve 16 and depresses the valve, the valve opensallowing a passage for the ink to flow from the refill unit 155 to theink bag 46. Due to the back pressure present in the ink bag 46, the inkis drawn into the ink bag due to the pressure differential and as theink bag 46 fills and expands with ink, the spring element 54 maintains aconstant force between the ink bag 46 and the retainer element 55,thereby also maintaining a constant back pressure within the ink in theink bag 46. This continues until the ink bag 46 reaches its maximumcapacity whereby the pressure of the ink present in the ink bag 46equalises with the pressure of the ink of the refill unit 155 and nomore ink is drawn from the refill unit 155.

Bag constrictor actuators 190 extend through the apertures 60 to pressthe upper constrictor collar 59 towards the lower constrictor collar 57to bow the side panels 58 inwards and constrict the bag 46. As discussedabove with reference to FIG. 12, the bag constrictor 43, re-establishesthe negative pressure in the ink bag 46 as the refill unit is removed,by releasing the constriction.

While the present invention has been illustrated and described withreference to exemplary embodiments thereof, various modifications willbe apparent to and might readily be made by those skilled in the artwithout departing from the scope and spirit of the present invention.Accordingly, it is not intended that the scope of the claims appendedhereto be limited to the description as set forth herein, but, rather,that the claims be broadly construed.

1. A printhead for an inkjet printer, the printhead comprising: aprinthead integrated circuit formed on a wafer substrate usinglithographically masked etching and deposition techniques; an integratedcircuit support structure for mounting in the printer adjacent a mediafeed path; and, a polymer sealing film between the integrated circuitsupport structure and the printhead integrated circuit for fixing theprinthead integrated circuit to the integrated circuit supportstructure.
 2. A printhead according to claim 1 wherein the polymersealing film is more than 25 microns thick.
 3. A printhead according toclaim 2 wherein the polymer sealing film is more than 50 microns thick.4. A printhead according to claim 3 wherein the polymer sealing film ismore than 100 microns thick.
 5. A printhead according to claim 2 whereinthe polymer sealing film is about 200 microns thick.
 6. A printheadaccording to claim 1 incorporated in a cartridge unit for an inkjetprinter, the cartridge unit comprising: an ink storage compartment andan ink feed system for connection to the printhead, the printhead havingan array of ink ejection nozzles, wherein the ink storage compartmenthas a variable storage volume and a displaceable wall section biased toexpand the variable storage volume to generate a negative pressuretherein, such that ink does not inadvertently leak from the ink ejectionnozzles.
 7. A printhead according to claim 1 arranged to be suppliedwith ink by a negatively pressurized ink storage compartment, the inkstorage compartment having an interface for receiving a refill unit forrefilling the ink, the interface having an inlet valve biased to itsclosed configuration, wherein the refill unit comprises: a bodycontaining a quantity of ink; engagement formations for releasablyengaging the interface; and an inlet valve actuator for opening theinlet valve as the refill unit engages the ink interface so that the inkin the body is in fluid communication with the ink storage compartment.8. A printhead according to claim 1 incorporated in an ink cartridgehaving a negatively pressurized ink storage compartment that suppliesink to the printhead, and an interface for receiving a refill unit forrefilling the ink the interface having a normally closed inlet valve anda normally open outlet valve, both in fluid communication with the inkstorage compartment, wherein the refill unit comprises: a bodycontaining a quantity of ink; and a docking portion having an ink outletand valve actuator formations, and wherein during use, the dockingportion releasably engages the interface to actuate the inlet and theoutlet valves so the cartridge fills with ink from the body because ofthe negative pressure in the ink storage compartment.
 9. A printheadaccording to claim 1 arranged to be supplied with ink by a negativelypressurized ink storage compartment which is arranged to be refilled bya refill unit via a normally open outlet valve, the refill unitcomprising: a body containing a quantity of ink; engagement formationsfor releasably engaging the ink storage compartment; and an outlet valveactuator for closing the outlet valve as the refill unit engages the inkstorage compartment.
 10. A printhead according to claim 1 arranged to besupplied with ink by an ink storage compartment which is arranged to berefilled by a refill unit, wherein: the printhead has an array ofnozzles; during use, the ink storage compartment is maintained at anegative pressure to avoid inadvertent ink leakage from the nozzles; therefill unit comprises a body containing a quantity of ink, an ink outletand a repressurizing arrangement; upon engagement of the refill unitwith the ink storage compartment, the repressurizing arrangement causespart of the unit to be inwardly depressed as the ink from the body isdrawn into the ink storage compartment through the ink outlet by thenegative pressure until pressure equalization; and upon subsequentdisengagement of the refill unit from the ink storage compartment, therepressurizing arrangement releases the inwardly depressed part of theink storage compartment to re-establish the negative pressure.
 11. Aprinthead according to claim 1 incorporated in an ink cartridge for aninkjet printer, the cartridge comprising: an ink storage compartmenthaving opposed wall sections connected by a flexible wall arrangement todefine a variable ink storage volume; and an ink feed system forsupplying for supplying ink to the printhead which has an array ofnozzles, wherein one of the opposed wall sections is displaceable andbiased to expand the variable ink storage volume to create a negativepressure in the ink storage compartment for avoiding inadvertent inkleakage from the nozzles.
 12. A printhead according to claim 1 arrangedto be supplied with ink by an ink storage compartment having aninterface for releasably engaging with a refill unit for refilling theink, the interface having valves for controlling ink flows into, and outof, the storage compartment, wherein the refill unit comprises: a bodycontaining a quantity of ink; an ink outlet; and valve actuators foractuating the valves when the refill unit engages the interface, suchthat the valve actuators actuate the valve in a predetermined sequence.13. A printhead according to claim 1 incorporated in an ink cartridgethat forms part of an inkjet printer, the printer having controlcircuitry and an interface for releasably engaging a refill unit forrefilling the ink cartridge, wherein the refill unit comprises: a bodycontaining a quantity of ink; an ink outlet; and a memory circuit forstoring information relating to at least one characteristic of the ink,and wherein, during use, the memory circuit allows to the controlcircuit to interrogate it to verify that the ink in the refill unit issuitable for the printer.
 14. A printhead according to claim 1, furthercomprising: a nozzle plate with an array of nozzles formed therein; anda printhead maintenance assembly comprising a capper to cover the arrayof nozzles when the printhead is not in use and a cleaner for engagingthe nozzle plate and wiping across the nozzles, wherein the cleaner ispositioned between opposing sides of the capper.
 15. A printheadaccording to claim 1, further comprising an array of nozzles, theprinthead being incorporated in an inkjet printer comprising: amaintenance assembly for moving between a capped position where theassembly covers the array of nozzles, and an uncapped position spacedfrom the array of nozzles; and a motorized drive for moving themaintenance assembly between the capped position and the uncappedposition.
 16. A printhead according to claim 1 incorporated in an inkcartridge in an inkjet printer, the ink cartridge having an interfacefor engaging an ink refill unit for replenishing the cartridge, whereinthe ink refill unit comprises: an ink storage compartment; a dockingportion for engaging the interface of the cartridge, the docking portionhaving a base plate with an ink outlet for connection to an inlet porton the interface; and engagement formations for releasably engaging theinterface, the engagement formations being formed on the transversecentre line of the base plate, the centre of the ink outlet being spacedfrom the transverse centre line.
 17. A printhead according to claim 1incorporated in an ink cartridge in an inkjet printer, the ink cartridgehaving an interface for engaging an ink refill for replenishing thecartridge, an ink storage compartment partially defined by a tubularflexible wall, and a constriction mechanism for constricting theflexible tubular wall by a predetermined amount, wherein the ink refillunit comprises: a body containing a quantity of ink; and a dockingportion for engaging the interface of the cartridge, the docking portionhaving an ink outlet for connection to an inlet port on the interface,and a plurality of constriction actuators for actuating the constrictionmechanism as the ink refill unit engages the interface and releases theconstriction mechanism as the ink refill unit disengages the interface.18. A printhead according to claim 1 incorporated in an ink cartridge inan inkjet printer, the ink cartridge having an interface for engaging anink refill unit for replenishing the cartridge, wherein the ink refillunit comprises: a body containing a quantity of ink; an ink outlet forengaging a complementary ink inlet in the interface; and a spigotextending from the body for insertion in an aperture in the interface,the lateral cross section of the spigot being keyed to the shape definedby the aperture to ensure the ink refill is correctly matched to thecartridge.
 19. A printhead according to claim 1 incorporated in an inkcartridge in an inkjet printer, the ink cartridge being arranged to bereplenished by an ink refill unit, the ink refill unit comprising: abody containing ink; an ink outlet for engaging a complementary inkinlet in the cartridge; and a visual indicator to provide a visualindication when a predetermined quantity ink has flowed from the refillunit into the cartridge.
 20. A printhead according to claim 1incorporated in an inkjet printer comprising: an outer casing with ahingedly mounted panel for access its interior; and a cradle housedwithin the outer casing for supporting an ink cartridge, the cradlehaving a hingedly mounted lid that opens to allow the ink cartridge tobe inserted and removed, wherein the hinge axis of the lid and the hingeaxis of the panel are parallel, and the lid and the panel both open inthe same direction.